What Is an Acceptable Co Reading at a Vented Gas Fireplace

SCOPE

This manual volition address both the presence of CO contained inside the combustion system, and its presence outside the combustion system which may be due to incorrect installation or maintenance, component failure, or external factors such as frazzle fans or air treatment equipment. Along with suggested action guidelines, it also provides the reader with an understanding of the operation of related measuring equipment.

TECHNICAL PROGRAMS
MAY 2018

CARBON MONOXIDE HANDBOOK

PDF Version

Table OF CONTENTS

• Definitions
• Introduction
• Attributes of Carbon Monoxide
• Carbon Monoxide Infiltration
• Factors Affecting Carbon Monoxide Absorption
• Carbon Monoxide Production
• Causes of Incomplete Combustion
• Venting Systems
• Building Depressurization
• Unvented Appliances
• Plugged or Damaged Oestrus Exchangers
• Carbon Monoxide Levels – Ambient and Flue Gas
• Ambient Carbon Monoxide
• Unrepairable Appliance
• Investigating Ambient Carbon Monoxide Causes
• Flue Gas Carbon Monoxide
• Carbon Monoxide Alarms
• Appendix "A"- Selected Canadian Gas Appliance Standards
• Appendix "B" - Suggested Method to Inspect the Heat Exchanger of a Residential Furnace
• Appendix "C" - Suggested Checklist for Depressurization

_{This material is owned by Technical Safety BC and protected by copyright law. Information technology may not be reproduced or redistributed without the prior written permission of Technical Safe BC.}

DEFINITIONS

Aldehydes

A class of gases formed by incomplete combustion of hydrocarbons. Aldehydes tin can produce a precipitous, metallic sense of taste in the oral fissure, and irritate the eyes and mucous membranes. If aldehydes are nowadays, at that place is a strong possibility carbon monoxide is likewise being produced.

Machine-ignition temperature

The lowest temperature of a substance at which information technology spontaneously ignites in a normal atmosphere without an external source of ignition, such equally a flame or spark.

Carbon monoxide

A colourless, odourless, very toxic gas (CO) that is formed as a product of the incomplete combustion of carbon or a carbon compound.

Carbon monoxide air-gratuitous

An "air-free" reading is calculated to decide what the CO concentration in flue gas would be if all the excess air were removed.

The CO reading is multiplied by the ratio of the atmosphere'due south oxygen percentage (twenty.ix) to the excess oxygen percentage in the flue gas.

The formula is

E.g.: If the measured CO is 50 ppm and the measured oxygen in the flue gas is 10.v%.

Category I apparatus

An appliance that operates with a nonpositive vent static force per unit area and with a flue loss not less than 17%.

Note

This category consists of draft-hood-equipped appliances, appliances labelled equally Category I, and fan-assisted appliances for venting into Type B vents.

Category 2 apparatus

An apparatus that operates with a nonpositive vent static pressure and with a flue loss less than 17%.

Category III appliance

An appliance that operates with a positive vent static pressure and with a flue loss not less than 17%.

Category IV appliance

An appliance that operates with a positive vent static pressure and with a flue loss less than 17%.

Dew point

The temperature (varying according to force per unit area and air content) beneath which water droplets begin to condense in a venting organization.

Flame impingement

The hitting of a burner flame confronting an object, such equally flame impingement on the heat exchanger.

Heat deflection temperature

Or heat distortion temperature (HDT, HDTUL, or DTUL) is the temperature at which a polymer or plastic sample deforms under a specified load.

Hemoglobin

(Hb or Hgb) is a poly peptide in red claret cells that carries oxygen throughout the torso.

Hydrocarbon

An organic compound (such equally benzene, methane, paraffin) made of 2 elements, carbon and hydrogen and found in coal, crude oil, natural gas, and found life. Hydrocarbons are used as fuels, solvents, and equally raw materials for numerous products such equally dyes, pesticides, and plastics; petroleum is a mixture of several hydrocarbons.

Lower explosive limit (LEL)

The minimum concentration of combustible gas or vapour in air, expressed equally a pct by volume, that will ignite if a source of ignition is present.

Luminous flame

A visible xanthous flame caused past a delay of carbon molecules finding oxygen and forming carbon dioxide. Luminous flames take a small-scale blue colour zone around the burner port due to the hydrogen. Hydrogen burns at a greater speed and a lower temperature than carbon does. The remaining bright yellow "luminous" area is the burning of carbon particles. The slow burning particles become semi-solid and because of their college temperature, produce an incandescent low-cal. The carbon particles complete their combustion when they reach the outer surface of the yellowish flame and find sufficient oxygen.

Stoichiometric ratio

The verbal ratio between air and combustible gas or vapour at which complete combustion takes place.

Thermal efficiency

This indicates the extent to which the energy added past the oestrus source (furnace, boiler, etc.) is converted to an output. Thermal efficiency can be field calculated provided the heating value of the fuel is known and accurate measurement of menses through the estrus exchanger is fabricated.

Upper explosive limit (UEL)

The upper explosive limit of a vapour or gas; the highest concentration of the substance in air that will ignite when an ignition source (heat, arc, or flame) is nowadays. At college concentrations, the mixture is too "rich" to burn.

Department 1

INTRODUCTION

For many gas fitters, carbon monoxide (CO) related contact most usually occurs afterward the triggering of a CO alert, which typically results in the attendance of either burn down/rescue services or a gas utility technician.

Customers utilizing propane and not serviced past a utility may contact a licensed gas contractor directly, as they may be the only bachelor technical resource.

This certificate provides information and guidelines for gas fitters and gas contractors to develop their own protocols for use when installing, servicing, or performing maintenance on gas appliances.

Testing for CO concentrations in flue gases, conditioned airstreams, and ambient atmospheres provides the gas fitter with of import data regarding the condition of the appliance's combustion organisation; informed analysis of CO levels and associated parameters will allow the gas fitter to make up one's mind if an apparatus is operating safely. The degree of thermal efficiency may also be assessed as office of a flue gas analysis.

This manual will address both the presence of CO contained within the combustion system, and its presence outside the combustion organization which may be due to incorrect installation or maintenance, component failure, or external factors such as exhaust fans or air handling equipment. Along with suggested action guidelines, it besides provides the reader with an understanding of the functioning of related measuring equipment.

Section two

ATTRIBUTES OF CARBON MONOXIDE

Carbon monoxide is produced from the incomplete combustion of fossil fuels and possesses the following physical backdrop:

Properties of Carbon Monoxide

Colourless	Cannot be seen.
Tasteless	Cannot be detected through the sense of sense of taste.
Odourless	Cannot be detected past sense of odor, However, CO tin also be accompanied by aldehydes. Aldehydes' odour tin can somewhat resemble vinegar, which can exist detected by the sense of smell, and may also effect in a metallic taste in the rima oris.
Non-irritating	Carbon Monoxide will not crusade irritation. However, aldehydes normally present with college levels of CO will irritate the optics, nose, and mucous membranes.
Specific gravity	Slightly lighter than air (Sg 0.975). It may, but non e'er collect near the ceiling, and mixes freely with air.
Flammable (explosive) limits	CO is flammable between concentrations of 12.5% to 74% when mixed with air. Its ignition temperature is 609ºC (1128ºF).
Toxic	Can cause death if plenty is captivated into the bloodstream.

Concentrations (*ppm) Observations and Health Effects

1 to iii	Normal.
25	Occupational exposure limit averaged over 8 hour catamenia.
30 to sixty	Exercise tolerance reduced.
100	15-minute short-term exposure limit (STEL).
60 to 150	Frontal headache. Shortness of breath on exertion.
150 to 300	Throbbing headache, dizziness, nausea, and dumb manual dexterity.
300 to 650	Severe headache; nausea and airsickness; confusion and plummet.
700 to g	Coma and convulsions.
1200	Immediately dangerous to life and health (IDLH).
1000 to 2000	Middle and lungs depressed. Fatal if not treated.
Above 2000	Speedily fatal.

*ane ppm = 1 function of gas per one thousand thousand parts air by volume

Carbon Monoxide Infiltration

Carbon monoxide is inhaled and captivated from the lungs into the bloodstream. Hemoglobin in the blood is responsible for transporting oxygen from the lungs to the body.

If given the pick, hemoglobin will link upwardly with carbon monoxide instead of oxygen. CO is absorbed into the bloodstream 250 times faster than oxygen, raising the level of carboxyhemoglobin very quickly. If this occurs, a lack of oxygen to the body will produce CO poisoning; CO asphyxiates the victim. If the blood oxygen is reduced enough, it can result in unconsciousness, brain damage or death.

CO POISONING SYMPTOMS

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Factors Affecting Carbon Monoxide Absorption

Some of the major variables that affect the amount of carbon monoxide absorbed into the body are:

• Concentration – The concentration of carbon monoxide in the free air.
• Exposure – The length of time an individual is exposed to CO.
• Concrete Activity – The higher the rate of respiration, the more carbon monoxide will be inhaled.
• Concrete Health – People that are ill, particularly those with eye or respiratory ailments, accept increased susceptibility. Individuals who smoke also take an increased susceptibility to CO.
• Age – Infants and the elderly are more susceptible to carbon monoxide.
• Sex – Females are more affected than males. If a women is pregnant, carbon monoxide can have an event on the fetus.
• Altitude – The higher the altitude, the greater the effect of carbon monoxide poisoning.

  CO absorbed in the bloodstream is cumulative. The healthy human being torso has difficulty removing carbon monoxide from the bloodstream and requires five hours to reduce the level by half. When physical health is compromised prior to exposure, the time needed to recover increases dramatically, and puts additional strain on the trunk'southward ability to process CO.

When a gas fitter is commissioning an apparatus, the process should include a discussion with the occupants regarding what is to be expected once the apparatus is operational.

The differences between a leak of natural gas (rotten egg – mercaptan odour), and other "gas smells" should be explained (see aldehydes), along with odours associated with the initial "burn in" of the appliance. Whenever a gas fitter is servicing a gas appliance, the occupants should be questioned regarding the operation of their appliances, and whatsoever reports of unusual odours, pilot outages, short cycling, etc. need to be investigated.

If an occupant complains of a "gas smell", it too needs to be determined if the odour is, in fact, related to unburned natural gas, combustion products, or an unrelated source.

Other signs which may bespeak CO is entering the living space include:

• Dead or dying houseplants
• Condensation on windows
• Discolouration effectually heating vents
• Discolouration or heat harm around the gas appli- ance burner compartment, including heat damage to wiring and external components
• Discolouration or oestrus damage around the draft hood of a vented apparatus
• Missing or incorrectly installed fan compartment doors on forced-air furnaces
• Plugged or missing combustion/ventilation air supplies
• CO alert has been or is sounding periodically
• Flames rolling out of combustion chambers
• Reports from commencement responders or medical personnel

CO poisoning is ofttimes mistaken for the flu or nutrient poisoning. Comments from occupants regarding ongoing illnesses that coincide with appliance usage are crusade for farther investigation. Remember that CO can also be produced from incorrectly performance oil furnaces, woodstoves, or fireplaces; any fuel-called-for device can produce CO under the correct conditions.

Allowing a vehicle to idle or using power equipment in a garage attached to a living space may allow CO to enter the occupied space. Propane powered generators can produce excessive amounts of CO without showing any outward signs, such as running rough, blackness, sooty frazzle.

Department 3

CARBON MONOXIDE Product

Complete combustion of natural gas or propane produces carbon dioxide (CO2), water vapour (H2O) and heat. When fossil fuels such as natural gas or propane burn incompletely due to a lack of an acceptable supply or mixing of oxygen to produce CO2, CO forms.

Natural Gas complete combustion:
CH4 + 2O2 = CO2 + 2H2O + Oestrus

Natural Gas incomplete combustion:
2CH4 + 3O2 = 2CO + 4H2O + Estrus

Propane complete combustion:
C3H8 + 5O2 = 3CO2 + 4H2O + Heat

Propane incomplete combustion:
2C3H8 + 9O2 = 4CO2 + 2CO + 8H2O + Heat

CO may besides exist produced by sources that use hydrocarbons other than a natural gas or propane appliance. These include:

• Solid-fuel (woods, pellet, or coal) fireplaces or stoves
• Kerosene or oil direct-fired infinite heaters
• Oil furnaces
• Charcoal barbeques
• Gasoline or diesel powered generators, pressure washers, pumps
• Motor vehicles

Causes of Incomplete Combustion

Complete combustion of natural gas or propane results in a sharp, blue flame, with an inner cone and outer envelope. Incomplete combustion due to inadequate air supply produces a soft, xanthous flame with poor definition. The yellow flame is composed of incandescent carbon particles which have not combined with oxygen molecules. They form soot when deposited on a solid surface. Orangish flecks appearing above a sharp blue flame should not exist mistaken for incomplete combustion; typically, these are the result of dust particles existence consumed by the flame.

Incomplete combustion may be caused by:

• Flame impingement, which occurs when a flame strikes an object and cannot extend far enough to complete the combustion process. Impingement disrupts the flame pattern, but may not produce a yellow, sooty flame. Dislodged burners or refractory, misplaced burn logs or decorative embers tin produce impingement.
• Overfiring or underfiring an appliance, either through incorrect manifold pressures or orifice sizing.
• Poor mixing of gas and air resulting from the wrong aligning of, or plugged or restricted, main air shutters.
• Plugged furnace heat exchangers, or boiler flue passages or coils.
• Missing, inadequate, or plugged combustion air supplies, or building depressurization.
• Restricted or blocked chimney flues, or the installation of undersized or incorrect venting.
• Recirculation of flue gases containing CO2 through a flame tin can crack the CO2, producing CO.
• Incorrect adjustment of some types of industrial burners may result in quenching of the flame caput.

Venting Systems

Flame Impingement

Although all appliance standards allow the production of limited amounts of CO, a properly performance venting organisation volition remove the combustion products to the outdoors. Damage to, or deterioration of, the vent can permit combustion products to enter the occupied infinite. Flue gas can enter buildings when gas appliances are sidewall vented close to adjoining occupancies.

Venting systems can exist damaged/compromised by:

• Mechanical impact or stresses
• Corrosion
• Temperatures in excess of the venting material'south certification rating range

Mechanical impacts may harm or dislodge vent connections; areas containing vents should non be used for storage.

Mechanical stress from incorrect support of the vent, or settling of the structure, can permit vent sections to separate. Plastic (S636) venting systems may separate if joints are not properly prepared prior to gluing, or if the incorrect glue or primer is used.

Consideration for expansion and contraction of the vent must be made in accordance with manufacturer's certified instructions. Plastic venting which is rigidly restrained may produce enough force to issue in damage to the vent system.

Flue gas condensate is acidic and corrosive. Appliances fastened to metal venting (other than ULC-609 Stainless Steel) must be designed, installed, and operated in a manner which limits "wet fourth dimension" within the vent. "Moisture time" refers to the period during operation when the products of combustion cool to the dew bespeak (approximately 125°F or 52°C), allowing condensate to form within the vent. Category III appliances are usually vented with stainless steel venting materials.

Signs of corrosion include rust staining of the vent, or appliance vent connection, or deposits of white crystals axiomatic on the vent; standard and mid-efficient furnace oestrus exchangers tin can too be damaged through excessive "wet time".

Typical causes include:

• Oversizing of the heating apparatus
• Underfiring of the appliance
• Wrong adjustment of thermostat heat anticipators
• Incorrect temperature rise through the apparatus
• Oversizing of the venting system
• Excessive employ of unmarried-wall vent connectors

A properly sized, installed, and maintained heating appliance connected to a B-vent or chimney liner limits the production of condensate.

If Category I appliances are common vented and ane appliance is removed at a afterward appointment, such every bit the replacement of a mid-efficient furnace to a high efficiency furnace, the existing venting must be verified to exist adequate for the remaining appliance(s). It is the gas fitter's responsibleness to ensure that the appliance is installed and operated in accordance with the manufacturer's certified installation instructions.

For forced-air furnaces, firing rate, manifold force per unit area, external static pressure (ESP), temperature rise, and heat anticipator values are typically specified by the manufacturer.

For boilers, manufacturer's specifications typically include firing charge per unit, manifold pressure, return h2o temperature, temperature rising, and water treatment requirements.

An apparatus or venting system showing signs of damage from corrosion warrants investigation into the underlying causes which resulted in the corrosion. Simply replacing the damaged components and walking abroad is irresponsible.

Signs of Corrosion

Category IV high-efficiency appliances (HEP's) have been vented with plastic pipage since their inception. HEP'south typically frazzle their products of combustion through plastic venting which has been assembled through a solvent welding process and is capable of withstanding positive vent pressures. Polypropylene venting materials are typically connected with a mechanical joining/locking system.

CO would but enter the occupied infinite if a failure were to occur in the appliance, venting, or if a CO-rich exhaust feather was directed or drawn into a building.

Prior to the revision of the Canadian Standard for Blazon BH Gas Venting Systems ULC-S636 in 2008, and the adoption of the 2010 CSA B149.1 installation lawmaking, apparatus manufacturers specified the apply of diverse types of plastic piping for venting their products. These types included older systems known as Plexvent, Selvent or Ultravent, ABS (both solid and cellular core), PVC, and CPVC.

Cellular core ABS was never an approved/accustomed venting material for use in British Columbia, merely noncompliant installations take been documented over the years. The electric current requirements of the ULC-S636-08 Standard, and the CSA B149.1 installation code, specify the listed systems bachelor for venting appliances based on the flue gas temperature. Technical Safety BC Directive "D-G5 070628 5 Revision: 05 Plastic Venting" further clarifies the requirements as well as requirements for previously installed existing systems.

It is the responsibility of the installing or servicing gas fitter to ensure that the venting system is appropriate for the appliance information technology is connected to, and that the apparatus continues to operate with a flue gas temperature not exceeding the listed value of the venting material.

Unsafe Venting

Elevated flue gas temperatures result from a reduction in heat transfer between the products of combustion and the heated medium (air or water). In water heaters and boilers, this may result from silting or scaling of the h2o side of the heat exchanger.

High return water temperatures or an aggregating of dirt on burner fan blades can also cause elevated flue gas temperatures.

For air-handling equipment, dirty or partially plugged filters, or accumulations of dust and dirt on the conditioned side of the oestrus exchanger may likewise lead to higher temperatures.

In both cases, the state of affairs compounds equally the appliance continues to operate for longer periods of time at the elevated temperatures in an attempt to satisfy the demand for heat.

Some appliances are now equipped with a high-temperature cut-out which senses the flue gas temperature at the outlet; service calls resulting from the functioning of the cutting-out need to include an evaluation of the atmospheric condition leading to the loftier temperatures.

Plastic venting which has been heated to its Oestrus Distortion Temperature (HDT) can soften and misconstrue. The degree of distortion is dependent on the temperature, duration, and degree of mechanical loading. Other signs of overheating include discolouration, and separation of pipage from the plumbing equipment socket. As with the activation of a high-temperature cut-out, a gas fitter must investigate the reasons leading to harm of the venting organisation.

Heat Baloney to Plastic Venting

Straight-vent heaters may let CO to enter the occupied space if the viewing or access panel(southward) are removed and not reinstalled correctly. Sealing gaskets which have deteriorated or are incorrect for the application too provide a path for combustion products to enter the space.

Never attempt to repair sealing systems with anything other than parts or products specified by the manufacturer.

Instructions regarding right assembly, torqueing of fasteners or curing of sealants, must be followed to ensure separation of flue products from the living space.

Circumspection

Never try to repair sealing systems with anything other than parts or products specified
by the manufacturer.
Instructions regarding correct assembly, torqueing of fasteners, curing of sealants, must be
followed to ensure separation of flue products from the living infinite.

Building Depressurization

Appliances which are non directly-vent can be affected by building depressurization, peculiarly at the showtime of a phone call-for-heat cycle. If adequate make-up air is non supplied, mechanical exhaust equipment (bathroom fans, kitchen fans, dryers, ventilators) may cause depressurization of the structure to the point where appliance vents are reversed and products of combustion spill inside the structure.

Combustion air supply systems are not sized to act as make-upwardly air for other sources of depressurization.

If another fuel-burning apparatus (oil furnace, wood stove, fireplace) is installed without its own acceptable air supply, information technology may reverse a natural gas vent to obtain sufficient combustion air.

Increasing the free energy efficiency of a building by weather-stripping doors, replacing windows and/or sealing air leaks without considering if adequate make-up and combustion air are available can pb to gas vents interim every bit air supplies rather than vents.

Occupants may deliberately block combustion air inlets in response to cold drafts. Calculation bathroom fans, or replacing a kitchen frazzle fan with a college-capacity model may as well lead to inadequate air supply.

A renovation which results in the appliances being isolated in a sealed room without sufficient combustion and ventilation air is a common cause resulting in appliance back drafting.

Depressurization may also occur within a mechanical room if render air ducting is poorly constructed or sealed, or service panels on the negative-pressure side of air handling equipment are missing or incorrectly secured.

Although natural-typhoon appliances are equipped with draft diverters which are designed to prevent downdrafts from entering the combustion bedchamber, a strong downdraft may actually interfere with burner functioning to the betoken of producing excessive CO.

At the kickoff of a heating bicycle, an atmospheric appliance will accept a significantly more difficult time establishing draft in the vent if it is opposed by cold outside air being fatigued down the vent through depressurization.

A common symptom reported to a gas fitter refers to "a pilot light that keeps going out on the h2o heater." In many cases, the initial assumption is a fault with the h2o heater'south pilot safety arrangement, leading to replacement of the thermocouple, pilot burner, gas valve, or the entire water heater. In many of these cases, the mistake is non with the water heater, but depressuriza- tion interfering with the stability of the airplane pilot light, main burner, or both. The safety system is actually functioning correctly; the crusade has been misdiagnosed

If a water heater is located close to a forced air furnace, and they are isolated in a mechanical room, depressurization can occur if the return-air ducting is poorly sealed and the furnace blower is operating. Incorrectly installed or missing filter access panels or filter rack caps can also produce the same result.

Remember that these conditions may only appear when the furnace room door is airtight; the trouble usually disappears when the doors are opened and the organization is allowed to balance with the rest of the structure.

Appliances with access from garages can be at risk for these atmospheric condition, equally the building regime require solid, tight-plumbing equipment doors with automatic closers to be installed at the access point. If these doors are not kept closed and in good repair, there is also the risk of exhaust gases from vehicles in the garage being drawn into the construction.

Central vacuum systems, although non unremarkably operated for ex-tended periods of time, usually take the power unit vented to the outdoors, or are located in a garage split from the living area.

Portable air conditioners are growing in popularity; when continued to provide cooling, they utilise an exhaust vented to the outdoors which will contribute to edifice depressurization.

As noted before, the operation of mechanical exhaust equipment can disrupt the venting of atmospheric gas appliances, oil furnaces, fireplaces, and woodstoves.

Typically, new construction has been evaluated past building code officials to ensure adequate combustion and make-upwardly air is provided to the structure; renovations and upgrades can result in a shortfall of replacement air which can touch the combustion and venting of atmospheric appliances.

Many homes are now equipped with estrus or energy recovery ventilators (HRV'south). HRV's increase energy efficiency and comfort levels past extracting warm, humid air from the living space and passing information technology through an air-to-air heat exchanger before exhausting it to the outdoors.

The HRV tempers incoming fresh air with heat scavenged from the exhaust flow. After installation, the HRV must be balanced in accordance with the manufacturer's instructions to ensure the amount of replacement exterior air is matched to the volume being exhausted. If the system is not balanced, or boosted mechanical exhaust is installed without allowance for increased make-up air (eastward.g., a larger capacity kitchen frazzle fan), depressurization may occur.

If the inlet air grille and filters are not maintained in accordance with the manufacturer's instructions and become restricted or blocked, the HRV will go an boosted mechanical exhaust, increasing the chances of downwardly drafting of atmospheric appliances.

As the majority of HRV's operate with a variety of fan speeds, it is of import to verify airflows as detailed in the manufacturer's instructions.

A gas fitter must be aware of the factors which may atomic number 82 to depressurization and its outcome on atmospheric appliances. Combustion and ventilation air supplies are to be checked for obstructions, whether deliberate, e.chiliad., "plugged past the occupant in order to stop a cold draft", or through lack of maintenance; an accumulation of debris on the inlet grille screen restricting or stopping the airflow.

A check for acceptable venting of atmospheric appliances requires:

1. All doors and windows to be airtight.
2. Solid fuel appliance dampers to be closed.
3. Atmospheric gas appliances shut downward. Appliances equipped with pilot lights may be gear up to the "Airplane pilot" position.

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HEAT RECOVERY VENTILATOR

1. Start up all mechanical exhaust equipment, and any other vented gas appliance(south).
2. Continuously monitor ambient air levels while performing this exam.
3. After five minutes, kickoff each atmospheric apparatus in turn. With a fume tube, taper, incense stick, or similar, check for spillage of outside air and/or combustion products at the typhoon hood and burner deck.
4. Monitor each draft hood for approximately five minutes to make up one's mind if venting is established.
5. Shut down mechanical exhausts, and render the atmospheric appliances to their normal states.

If correct venting is not established due to the furnishings of mechanical exhaust, sufficient make-up air must be added to the structure. Depending on the local building say-so, the air may have to be tempered through the utilise of a duct heater or fan-roll. The gas fitter must have steps in the acting to ensure appliances vent effectively. Options include disconnection or securing of circuit breakers controlling exhaust fans or dryers, or the blocking of windows in positions to provide temporary air supplies.

NOTE: See Appendix "C"

HVAC industry professionals may be utilized to perform additional testing to determine effective permanent make-up air solutions. Natural Resources Canada, in partnership with the Heating, Refrigeration, and Air-conditioning Establish of Canada, have created the Residential Air System Pattern Technician (RASDT) and Residential Hydronics Pattern Technician (RHDT)

Designations. Individuals property these designations have been certified in the pattern and commissioning of residential ventilation systems, and can provide analysis and advice on the effects of depressurization on a structure. Local building authorities may besides provide data on resource available inside their jurisdictions.

The Canadian Standards Association (CSA) Group (with input from regulators), the HVAC industry, and other interested parties, have produced a new Canadian standard: F300-xiii Residential Depressurization. This standard describes a method to identify when residential depressurization can cause a health take a chance, and provides solutions to prevent or mitigate the buildup of products of combustion within the house. The standard is available for purchase through CSA's website: Shop CSA - Standards.

Unvented Appliances

Cooktops, ranges, and ovens are capable of generating excessive CO, especially if the equipment is in poor repair, or is used incorrectly. Unvented cooking appliances should NEVER be used for infinite heating, and should be serviced regularly.

Exhaust fans should be used when the appliance is in operation, and the fan should be vented to the outdoors. Placing pots or griddle plates on stove top burners will produce a maximum corporeality of CO while the pot and contents heat up. One time the cooking temperature is reached, the amount of CO generated drops considerably. Oven pans must be kept clear of foil every bit the foil may obstruct secondary air openings to the burner and cause excess CO to exist produced.

Range burners should never be operated without the right support grates in place; using grates other than what is specified by the manufacturer can cause excessive impingement and/or quenching of the flame. Lazy, yellow, luminous flames betoken a problem with burner operation.

Possible causes include:

• Wrong oversized orifice installed
• Adjustable spud orifice has been set for natural gas; appliance is operating on propane
• Incorrect manifold pressure
• Wrong supply system pressure
• If equipped with a primary air shutter, the shutter is not sufficiently open, or the ports are blocked with lint or droppings
• Damaged, warped, or missing spreader confined on oven or broiler burners
• Installation of a replacement burner which does not meet the manufacturer's specifications

Plugged or Damaged Rut Exchangers

PLUGGED AND CORRODED BOILER Estrus EXCHANGER (Click to enlarge)

Appliance oestrus exchangers, whether air-to-air, or air-to- liquid, require regular inspection and maintenance to operate safely and efficiently. In some cases, errors in the installation or configuration of the apparatus may need to be corrected in order to provide safety, dependable performance moving forward.

If a gas fitter discovers an appliance with a significantly obstructed heat exchanger, additional investigation is required to make up one's mind the root cause(s) leading to plugging. The customer should be asked relevant questions, and appliance records should be examined, to provide background information on:

• Frequency of service
• Quality and blazon of service performed
• Attendance of utility (Fortis, etc.) technicians
• CO alarm activation (if present in the occupancy)
• Attendance of First Responders
• Complaints of illness indicating CO exposure

Atmospherically-vented boilers or hot water heaters (HWH), specially low-mass finned tube, are susceptible to plugging on the burner side if systems are not correctly designed, installed, operated, and maintained. Combustion-side restrictions lead to a cascading outcome which can result in a significant amount of CO being produced by the appliance.

Scaling or silting on the water side of a boiler or HWH may lead to customer complaints of high gas bills, lack of hot water, lack of oestrus within the infinite, or tripping of condom limits.

Reduction of heat transfer on the combustion side can likewise produce the same complaints, merely with the addition of a pregnant take a chance.

Restricted or plugged flue passages pb to incomplete combustion and CO production. With the apparatus unable to provide the amount of heat required to satisfy demand, it continues to operate in an attempt to satisfy the call

for oestrus. This typically results in elevated CO production until the flue passages are plugged to the bespeak where the flame-rollout switch (if nowadays) opens, or the control wiring is damaged past heat and flames and the gas valve is disabled. This scenario is cited in many cases involving CO fatalities.

Boilers which provide domestic, pool or spa heating, as well every bit space heating are susceptible to these conditions year- circular, non just during the heating season.

Points for the gas fitter to consider when analysing a plugged heat exchanger on a boiler or HWH:

• Is the inlet or return h2o temperature within the manufacturer's specifications? Water temperatures below required minimums can lead to condensation and scaling on the burn down-side of heat exchangers.
• Is the appliance equipped with an internal featherbed to maintain the required temperature rise? If and then, is it func- tioning correctly? Scale, sludge, or mechanical failure can crusade these to quit working, and let excessive amounts of cool water into the boiler.
• Has a manual bypass been installed? If then, has it been adjusted to maintain an acceptable temperature rise through the boiler?
• Has the apparatus been installed in accord with the manufacturer's certified instructions? In many cases, the manufacturer requires the use of heat exchangers to isolate the boiler from excessive amounts of cool water passing through the coils.
• Is the firing rate correct? Underfiring can produce extended periods of condensing, leading to scale buildup on the coils.
• How make clean is the combustion air supplied to the appliance? Are there excessive amounts of lint or pet dander being drawn into the combustion chamber? Not only can the debris plug master air ports on an atmospheric banality, or deposit in the coils, it can too foul inducer fans on the downstream side further reducing efficiency and affecting the combustion process.

Points to consider when analysing a plugged or damaged rut exchanger on a forced-air furnace:

• Does a visual inspection of the heat exchanger(s) reveal holes, rust staining or separated seams?
• Is at that place soot present on exchanger surfaces?
• Is the flame pattern on an atmospheric furnace disrupted when the circulating fan operates?
• Is there increased CO over ambience air present in the circulating airstream as measured at hot-air outlets?
• Is there bear witness of flame roll-out, or heat damage, at the burner compartment?
• Are the temperature ascension and static pressure across the heat exchanger within the manufacturer'due south specifications?​​Note: See Appendix "B"​

SECTION iv

CARBON MONOXIDE LEVELS – AMBIENT AND FLUE GAS

Ambience Carbon Monoxide

Flue gas analysis is a diagnostic tool which provides the gas fitter with important data regarding the safe and efficiency of a gas appliance.

All appliance standards include a maximum corporeality of CO which may be produced past an apparatus; the most current values are included in Appendix "A" at the end of this document.

Although in that location is less risk of CO entering the occupied space from a sealed-combustion appliance, testing is required to confirm the apparatus is operating as intended past the manufacturer, and that frazzle gas temperatures and CO content are at acceptable levels.

Care must exist taken that flue gas containing excessive CO is not fatigued into an occupied space through open windows and doors, or air handling equipment.

A gas fitter responding to a customer call regarding CO must first ensure their own prophylactic prior to entering the occupied space or mechanical room.

Typically, a utility technician or burn personnel will be the first on-scene, and will deal with the immediate life-safety issues. In outlying or unorganized areas, the gas fitter may exist the only technical resource available, and may exist chosen upon to manage all aspects of a CO emergency.

CAUTION

If the gas fitter suspects their client is being exposed to CO, advise them to:

• Call 911 or their emergency number – if available.
• Open all doors and windows.
• Go fresh air immediately outside.
• Seek medical attention if needed.
• Turn off any appliances that they doubtable are faulty.

A gas fitter must determine the safety of the environment they are planning on inbound.

Personal gas monitors are available either equally a unmarried CO gas monitor or a multi-gas monitor tin be purchased with CO as i of the selected gases. Common options are Oxygen, CO, Hydrogen Sulfide, and Flammable Gas (Lower Explosive Limit).

The Canadian Standards Association (CSA) C22.two NO. 152- M1984 (R2016) - Combustible Gas Detection Instruments standard is a recognized standard for monitors used in Canada.

CO Detector (Click to enlarge)

A combustion analyzer may as well be used to make up one's mind the air quality in the infinite. Gas sampling tubes and pumps (either manual or automatic) are also an option. Sampling tubes accept the reward of non requiring calibration or bump testing prior to employ, and at that place are no sensors to supersede.

Regardless of which arrangement is used, the gas fitter must follow all of the instructions provided by the manufacturer regarding storage, calibration, training, maintenance, and repair.

Any measuring or monitoring device must be zeroed in clear outside air prior to testing being performed inside a structure. Failure to do then may result in serious injury or death. Carbon monoxide is commonly referred to as "The Silent Killer".

WorkSafeBC (WSBC), through Section v.48 of the Occupational Health and Rubber Regulation, has set up the 8 hour fourth dimension weighted average (TWA) for CO at 25 parts per million (PPM). Eight-hr TWA is defined as "the time weighted average (TWA) concentration of a substance in air which may not be exceeded over a normal eight hour work period". WSBC'southward short term exposure limit (STEL) is 100 PPM. STEL is defined as "the fourth dimension weighted average (TWA) concentration of a substance in air which may not be exceeded over whatsoever fifteen minute period, limited to no more than than four such periods in an eight-hour work shift with at least ane hour between any two successive xv minute excursion periods".

Caution

Upon entering the edifice, the gas fitter must test for CO. If an ambience CO level is measured at more than 100 PPM, the gas fitter must leave the area and notify any affected occupants while leaving the building. The gas supply must be turned off outside the edifice. Local emergency services must be notified. The gas fitter may attempt to evacuate the edifice, but must not expose themselves to CO levels to a higher place 100 PPM, regardless of duration.

If the readings throughout the building are less than 10 PPM, and the gas appliances and other sources such as vehicles, wood or coal fireplaces, smoking or barbeques, have been eliminated equally the source of CO, the CO levels may be considered as acceptable.

If ambient air testing at any location inside the building indicates a CO level between ten and seventy ppm, the edifice should be ventilated and evacuated until the CO source has been eliminated.

If ambient air CO levels are between 71 and 100 ppm, and gas appliances are the suspected source, the gas fitter must shut off the gas supply to the appliances and attempt to ventilate the building. Local emergency services may exist required to appraise the need for evacuation. The gas fitter must minimize the fourth dimension spent working in these weather condition, as the STEL is fifteen minutes for a CO level of 100 ppm.

Unsafe Appliance (Click to overstate)

A gas appliance that produces CO levels in ambient air must be investigated to decide if the cause tin can be corrected prior to the gas fitter leaving the site. If not, the appliance is to be shut-off, the reasons explained to the occupant(south), and the advisable jurisdiction notified in accordance with section 54 of the Gas Safety Regulation:

Unrepairable Appliance

54 (1) A person who finds any apparatus or gas equipment across repair or in an unsafe condition must

(a)place the appliance or gas equipment out of service, and

(b) promptly notify a safety officer of its condition and location.

54 (two)If the initial notification under subsection (i) (b) is verbal, it must exist promptly confirmed past a written statement setting out the facts.

Reporting requirements are detailed in Data Bulletin: NO: IB-GA 2017-03 "Incident and Hazard Reporting to Technical Safety BC Gas". This bulletin is bachelor on Technical Safety BC's website. Occupants exhibiting signs of CO exposure should be referred to emergency medical services to determine the severity of their exposure, and the degree of treatment needed.

Investigating Ambient Carbon Monoxide Causes

Prior to inbound the building, ensure the measuring device has completed its calibration in fresh air. Learn more from the client regarding whatsoever circumstances leading to the suspicion of CO exposure. Other sources of CO demand to be investigated, such equally:

• Solid fuel fireplaces and stoves
• Barbecues (natural gas, propane, and charcoal)
• Fastened garages and idling vehicles
• Candles
• Smoking habits and frequency

The gas fitter should assess each gas appliance in turn, without making any adjustments or changes. Appliances, their venting systems, and combustion/make-up air supplies are to be examined for issues and possible rubber hazards which may be causing CO to enter the occupied space.

Refer to previous sections of this transmission for data regarding building depressurization and venting bug.

Ovens and range tops discharge flue gases directly into the living space. An oven may have a flue gas sample taken from the flue outlet as follows:

1. Gear up the temperature to 177ºC (350oF), allow the oven to attain temperature and begin cycling.
2. The oven should wheel for at to the lowest degree five minutes.
3. Insert the analyser'due south probe as far as possible into the outlet and sample the gases for an additional five minutes, or until a stable reading is recorded.

Range elevation burners can have their combustion products sampled with the probe held above the burner at a point where excessive estrus volition not damage the probe.

If a gas range is suspected of producing ambience CO levels in backlog of 10 ppm, farther investigation is needed. If an oven'south flue gas sample is greater than 400 ppm later warm-upwards, the gas supply must be shut off every bit per the "Unrepairable Appliance" department noted previously.

A reading less than 400 ppm, but greater than 250 ppm indicates the oven is in need of service or repair, and should be addressed. Readings less than 250 ppm also suggest service should be performed to reduce CO levels. All occupants should be advised that the exhaust fan (if vented to the outdoors) should exist in performance while using the oven and/or range tiptop burners. If an exhaust fan is a recirculating blazon, or no exhaust fan is installed, a window in the same space as the apparatus should be open while using the oven or range.

Flue Gas Carbon Monoxide

Flue gas analysis is important in helping the gas fitter determine the relative condition of a gas appliance, and whether at that place are issues resulting in the excessive production of CO.

Flue gases have a more direct path into the occupied infinite from appliances which are not direct-vent, just this should non allow the gas fitter to ignore CO levels exterior of manufacturer's (or the certification standard's) limits.

Excessive CO in a sealed-combustion appliance usually points to problems with the combustion system which can reduce efficiency and/or heating capacity, significantly shorten the life of the appliance, and damage components or the venting system.

Plugged or restricted flue passages or chimneys, or edifice depressurization, tin issue in flue gases entering the living space. Vented appliances must effectively remove all combustion products to the outdoors, regardless of whether or non they contain CO.

Whenever the manufacturer provides set-up instructions and/or target combustion efficiency parameters, the appliance shall be adjusted to those values. Manufacturers typically build in a safe cistron to their values to establish a buffer betwixt normal operation and potentially unsafe or damaging performance.

Attempting to "tweak" additional efficiency from an apparatus by reducing excess air towards the stoichiometric ratio can result in the production of big amounts of CO if fuel/air mixing deteriorates, or the amount of combustion air delivered to the burner is reduced through dirt buildup on fan blades, airboxes or louvers.

Carbon Monoxide is combustible at the lower explosive limit (LEL) of 12.5% and has an ignition temperature of 609ºC (1128º F). An additional hazard is the possible germination of gratis hydrogen gas during the incomplete combustion process.

Hydrogen has an LEL of 4% and will auto-ignite at 495ºC (923º F). Care must be taken to ensure adequate excess air is bachelor for the combustion process. The presence of oxygen in flue gases is an important indicator of adequate combustion air.

Sampling of combustion gases needs to take place as close to the combustion sleeping accommodation as possible, and without the addition of dilution air from typhoon hoods or barometric dampers.

Depending on the fashion of sampling probe, it can either be dropped down the typhoon diverter opening towards the combustion chamber, or inserted through a pigsty drilled in the flue collar as close as possible to the chamber. For furnaces with clamshell style rut exchangers, a sample can exist taken from the acme of each flue passage.

For mid-efficiency appliances equipped with inducer fans, the sample can be taken from a pigsty drilled in the flue collar/vent connectedness. Many manufacturers of high-efficiency appliances are now including sampling ports on the flue outlet; some are also including a port on the combustion air inlet plumbing fixtures.

If a manufacturer includes combustion analysis values in their installation/servicing instructions, an accessible sampling signal must exist provided.

S636 certified plastic venting systems provide "access tees", which include a ½" FIP branch and plug. A standard S636 tee can also exist used, with the employ of a bushing with a ½" FIP tapping.

CARBON MONOXIDE HANDBOOK Section 4 | CARBON MONOXIDE LEVELS CONT.

A condensate tee should not be used, equally condensate draining out of the tee tin flood the analyser's trap, causing nuisance shutdowns and possibly dissentious the instrument.

If a manufacturer does non specify combustion analysis values, the following tin can be used every bit a general guide:

	ATMOSPHERIC DRAFT Apparatus	INDUCED Typhoon APPLIANCE	CONDENSING APPLIANCE (90%+)	Ability BURNER
O2	4% - nine%	seven% - nine%	5% - 7%	three% - 6%
CO2	6.5% - viii%	6.5% - 8%	7% - 8.5%	8.five% - 11%
STACK TEMP.	163ºC - 260ºC (325ºF - 500ºF)	163ºC - 204ºC (325ºF - 400ºF)	< 52ºC (125ºF)	160ºC - 299ºC (320ºF - 570ºF)
Typhoon	-0.02" wc - -0.04" wc	-0.02" wc - -0.04" wc	As per manufacturer'due south specifications	Every bit per manufacturer'due south specification
CO	< l ppm air-complimentary	< fifty ppm air-complimentary	< 50 ppm air-gratis	< 100 ppm air-free

SECTION 5

CARBON MONOXIDE ALARMS

CAUTION

CO alarms can provide an boosted level of protection for occupants where fuel-called-for appliances are located. They are not a substitute for regular inspection and maintenance of gas appliances by qualified gas fitters, but do provide extra monitoring in-between service intervals. They are also non a substitute for smoke alarms, although some manufacturers are now producing models which combine both functions in a single unit.

Carbon Monoxide Testing

The BC Building Code requires CO alarms to be installed in new construction where fuel called-for appliances are installed. The Metropolis of Vancouver is the only jurisdiction in the province requiring CO alarms in all residential occupancies that incorporate a fuel burning apparatus and/or an fastened garage. Exterior of Vancouver, in that location is no requirement for alarms to be installed in dwellings built prior to the changes to the Building Code.

It is strongly recommended that all occupancies with gas- fired appliances install CO alarm(south) in accordance with the current BC Edifice Lawmaking specifications:

• CO warning(s) installed in every bedroom or within five meters (16 anxiety) of each bedroom door.
• If a fuel-burning appliance, such as a fireplace, is located inside a bedroom, the CO alarm should be installed inside the bedroom.
• The CO alarms shall:
  • Conform to Tin/CSA 6.19, Residential CarbonMonoxide Alarming Devices
  • Be equipped with an integral alarm that satisfiesthe audibility requirements of Can/CSA half dozen.xix
  • Be bombardment operated or hardwired, and
  • Have no disconnect switch betwixt the overcurrentdevice and the CO alarm, where the CO alarm is powered by the dwelling unit's electrical arrangement, and
  • Be mechanically fixed at a tiptop every bit per manufacturer'southward recommendations
• Units combining smoke and CO alarms are adequate

CAN/CSA half dozen.nineteen is the recognized Canadian standard for CO alarms intended for use in ordinary locations in residential

occupancies. This includes dwelling units, recreational vehicles and mobile homes, and unconditioned areas. The recognized Canadian standard for multi-criteria smoke alarms (which combine smoke and CO detection in a unmarried device) is CAN/ULC S531. With these devices, the CO alarm portion must meet CAN/CSA 6.19. E'er look for the list information on the device and its packaging, locate and install information technology in accordance with the manufacturer's instructions. Also, examination and maintain the device as directed in the instructions; these devices accept a service life and volition need replacing on or before the appointment marked on the unit of measurement.

If an alarm fails to operate correctly when the exam push is pushed, refer to the troubleshooting section in the transmission. An alarm which is not operating correctly, or displaying an "stop of life" bulletin will not respond to CO and must be replaced immediately.

CO alarms audio different from smoke alarms when they activate. By introducing a new emergency device into the domicile, information technology is important that everyone in the household knows the departure between an alarming smoke alarm and an alarming CO alarm. According to the CO alarm standard, a CO alarm bespeak consists of four very quick beeps followed by a v second pause and the pattern is repeated.

This contrasts with a smoke alarm's bespeak as divers by the fume alarm standard CAN/ULC S531, which consists of three beeps followed by a 1.five second break, and and so this pattern is repeated.

Occupants need to know the difference betwixt an actual warning sound versus the low bombardment or end of life warnings for both their smoke and CO alarms. Owners should consult their instruction manual to obtain further data on the characteristics of the audible and/or visual signals for each device.

Caution

CO alarms can provide an additional level of protection for occupants where fuel-burning appliances are located. They are not a substitute for regular inspection and maintenance of gas appliances past qualified gas fitters, merely exercise provide extra monitoring in-between service intervals. They are also not a substitute for smoke alarms, although some manufacturers are now producing models which combine both functions in a unmarried unit.

SECTION 6

APPENDIX "A"

Selected Canadian Gas Appliance Standards

Annotation that the values given beneath are "maximum" levels; the gas fitter should attempt to adjust and tune each appliance to produce the minimum corporeality of CO while still keeping the adjustments in line with the manufacturer'southward certified instructions.

Allowable CO Levels

CSA NUMBER	CURRENT CANADIAN STANDARD	AN Appliance SHALL Non PRODUCE A CONCENTRATION OF CARBON MONOXIDE IN Backlog OF:
ANSI Z83.25-2017/CSA 3.19-2017	Direct gas-fired process air heaters	5 ppm Maximum Average Concentration added
ANSI Z21.xiii-2017/CSA 4.9-2017	Gas-fired low pressure steam and hot water boilers	400 ppm air-free
ANSI Z21.88-2016/CSA two.33-2016	Vented gas fireplace heaters	200 ppm air-complimentary for gravity vent and 400 ppm air-free for directly vent and power vent appliances
ANSI Z83.11-2016/CSA one.8-2016	Gas food service equipment	800 ppm air-gratis
ANSI Z21.47-2016/CSA ii.3-2016	Gas-fired fundamental furnaces	400 ppm air-free
ANSI Z21.60-2017/CSA two.26-2017	Decorative gas appliances for installation in solid-fuel burning fireplaces	400 ppm air-free
ANSI Z21.5.1-2016/CSA seven.1-2016	Gas apparel dryers, volume I, type 1	400 ppm air-free
ANSI Z83.8-2016/CSA two.half dozen-2016	Gas unit heaters, gas packaged heaters, gas utility heaters, and gas-fired duct furnaces	400 ppm air-free
ANSI Z21.10.3-2015/CSA 4.three-2015	Gas-fired water heaters, book III, storage water heaters with input ratings above 75,000 Btu per 60 minutes, circulating and instantaneous	400 ppm air-free
ANSI Z21.one-2016/CSA 1.ane-2016	Household cooking gas appliances	800 ppm air-costless
ANSI Z83.4-2017/CSA three.7-2017	On-recirculating directly gas-fired heating and forced ventilation appliances for commercial and industrial application	v ppm Maximum Average Concentration added
ANSI Z21.58-2015/CSA 1.6-2015	Outdoor cooking gas appliances	800 ppm air-gratis
ANSI Z21.97-2014/CSA 2.41-2014	Outdoor decorative gas appliances	800 ppm air-free
ANSI Z21.86-2016/CSA two.32-2016	Vented gas-fired space heating appliances	200 ppm air-free
CAN1-3.ane-77 (R2016)	Industrial and commercial gas fired packet boilers	400 ppm air-free
ANSI Z83.7-2011/CSA two.14-2011 (R2016)	Gas-fired construction heaters	200 ppm air-free

APPENDIX "B"

Suggested Method to Audit the Estrus Exchanger of a Residential Furnace

Primary and Secondary Heat Exchanger

The main estrus exchanger in a furnace can be made from rolled steel of 2 mirror image parts seamed together like a clam vanquish or utilize tubing. Condensing furnaces will use a device that looks similar to a machine radiator for the secondary oestrus exchanger.

wheel to its off position when the temperature of the air in the plenum exceeds the limit set by the technician.

Plugged air filters accelerate heat exchanger failure. A furnace filter neglected for several heating seasons will block the period of air through the heat exchanger. The internal temperature of the furnace may exceed the continuous operating design temperature without reaching the high limit setting. Broken welds and cracks may result.

A notable number of heat exchangers have been known to neglect from aberrant rust accelerated by the presence of chlorinated compounds. A chlorinated compound is any compound to which a chlorine molecule is attached. Many household products are chlorinated such equally detergents,

bleach, solvent and pigment thinners. When these compounds mix with humidity, hydrochloric acid is formed and is drawn into the furnace where the acid produces rust and salt deposits. The salt deposits re-combine with moisture from the air to continue the corrosive procedure and rapidly ruin a heat exchanger.

Rust may occur due to condensate leaks onto the heat exchanger from an air conditioner roll, from humidifier leaks, or simply from location of the furnace in a damp or wet location.

Steps involved for inspecting a furnace's heat exchanger:

Many furnaces neglect by developing cracks in the sheet metal, cracks along welded seams, or holes due to rust or corrosion.

Heat exchangers can fail by becoming overheated. The heat exchanger is protected from overheating by a advisedly adjusted high limit. The high limit causes the furnace to

1. Wait for flame disturbances.

Start the furnace and detect whatsoever changes in the flame pattern as the circulating air blower starts operating. Expect for floating flames, flame roll-out or flame distortion. These atmospheric condition bespeak a possible split seam, open crack, severe deterioration of the heat exchanger or gasketing material, or concrete separation of the connected parts. If a flame disturbance occurs after the blower comes on, it is a good indication that a problem may exist in the lower portion of the heat exchanger (up-flow furnace). If this is the example, proceed to Footstep 4.

NOTE: Ensure that there are no exterior drafts that could be causing the flame disturbance.

1. Measure CO levels in the airstream.

With the furnace operating, measure out the CO level in the return air duct near the furnace and record the value. Adjacent, measure the CO level in the supply ducting leaving the furnace. Record this value. If in that location is no measurable difference in the CO level in the return and supply airstreams, it is probable the furnace is not leaking CO into the airstream. If the CO in the supply air ducting is greater than the CO in the return air, it is likely that the furnace is supplying the CO through the heat exchanger. If this scenario is encountered, proceed to Step iv.

1. Measure out oxygen levels in the vent.

Induced typhoon furnaces are less likely to leak products of combustion into the circulating air stream than a natural draft furnace due to the negative pressure level inside the heat exchanger created by the inducer fan. Insert the flue gas analyzer probe into the vent. Find the oxygen level. If a significant increase occurs when the circulating fan is energized, it is possible that the heat exchanger is damaged. Go along to Stride 4.

1. Visually inspect the heat exchanger.

Occasionally holes formed by rust or cracks tin exist seen with the eye or with the assistance of a mirror, but often only 20% of the total surface of the heat exchanger is visible to view, fifty-fifty with a mirror once a furnace is installed.

Some holes or cracks are visible only when thermal expansion causes the cracks to open, which can be difficult to observe when the furnace is operating. If the furnace fails any of the three preceding steps,conscientious attention should be made to the visual inspection. This may require the removal of the circulating fan to see the lesser of the heat exchanger and cutting an access door into the supply plenum to see the top of the heat exchanger. Pay particular attention to welds, seams, joints and discoloured spots on the heat exchanger(southward). If the burners are removed, a flashlight may be directed into each heat exchanger and visually inspected from the exterior, looking for signs of light. If available, an inspection photographic camera could exist inserted into each heat exchanger.

Code Rule 4.21 of the CSA B149.1 Gas code lists requirements that must be followed if a heat exchanger is institute to be lacking.

APPENDIX "C" - SUGGESTED CHECKLIST FOR DEPRESSURIZATION

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Source: https://www.technicalsafetybc.ca/guidelines-gas-service-industry-carbon-monoxide

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