CO standards and guidelines

What standards do I use if local codes do not address this issue?

Two circumstances must exist to make carbon monoxide a hazard:

·        It is produced in concentrations that can affect health or hurt someone..

·        An open path exists for CO to reach people.

Carbon monoxide has a natural tendency to rise in temperatures normally found inside buildings.  At freezing temperatures, carbon monoxide is heavier than air.  Please keep in mind that cold days in areas of high automotive activity, out door ambient CO levels may be more noticeable than on days above freezing.

Other combustion by-products can contribute to poor health symptoms even when CO is not produced.  These by-products include NO_X gases and excessive CO₂.  Acidic moisture from combustion gases can also be harmful.

Though carbon monoxide is odorless, a distinct pungent odor can occur (but not always) during incomplete combustion.  Aldehydes are a by-product of incomplete combustion and come with this pungent odor.  Often times this odor is mistaken by the consumer as a gas leak.  Auto exhaust may also have an odor of raw fuel. 

The deceiving part about carbon monoxide is that it does not have an odor. 

Carbon monoxide is given off by the incomplete burning of solid, liquid or gaseous fuel.  This occurs when there is not enough oxygen mixed with the fuel and/or proper combustion conditions are not met.  Variation in combustion conditions can result in varying levels of CO.

What is the fuel being used?  How many BTU’s per cubic foot is there or how many BTU’s per gallon?  We have to know the fuel.

IN GAS OR OIL BURNING SYSTEMS, PROPER COMBUSTION CONDITIONS INCLUDE:

1.                  Flow of fuel is specific – measure it.  Measure in water column inches or PSI (Pounds per square inch).  Always check manufacturer specifications.

2.                  Air and fuel mixtures – measurable.  Combustion analyzers offer O₂, CO, flue-stack temperature measurements.  CO₂, efficiency and CO air free are calculations. Combustion air is adequate, to code and does not interfere with combustion systems performance.

3.                  Fuel burns completely, without impingement or interference – minimal CO production.

4.                  Systems with vents shall draft without interruption and installed as specified in accordance to vent manufacturers sizing, installation and performance requirements.

Is this CO problem identifiable and is it correctable?  Do we need to vacate the premises?  Do I have a duty to report this level to an Authority?  

Our procedural steps should include rating the levels found and referencing them to reasonable and accepted levels.  Many standards for CO exposures come from nationally recognized professional associations or governmental administrative organizations.  The medical community has helped establish these levels.  All standards are current as of the issue date (2/01) of this publication.

Many local Authorities of Jurisdiction have living space limits for carbon monoxide.  It is recommended you ask the local fire department what their limits are for evacuation

In some locations, the regulated gas utility may be the Authority, or the city, county, state inspection department may be. 

ASHRAE (62-89) (American Society of Heating, Refrigeration and Air Conditioning Engineers)

009 PPM:  The maximum allowable concentration for continuous (24 hr) exposure.  ASHRAE states the ventilation air shall meet the out door air standard.

EPA (Environmental Protection Agency)

009 PPM:  This level or lower as an ambient air quality goal averaged over eight (8) hours. This out door air standard is exceeded in many urban areas due to auto exhaust.

Common Action Level

009 PPM or more above what you measured outside is the most common action level in the U.S. by local Authorities of Jurisdiction for further testing.  Some jurisdictions require fuel shut-off until problem diagnosed and corrected.

BPI  (Building Performance Institute)

10 to 35 PPM is a marginal level in reference to potential or foreseeable problems in some situations.  Occupants should be advised of a potential health hazard to infants and small children, elderly people and persons suffering from respiratory or heart problems.  If building has attached auto garage, document CO levels in garage.  Accept this level as normal where unvented appliances are in use.  These levels are unacceptable when originated from vented appliances.

EPA

035 PPM:  This level or lower as an ambient air quality goal averaged over one (1) hour.          

Common Action Level

035 PPM is also a common action level for fire department or other emergency responders to utilize self contained breathing apparatus when occupation of that environment is to be sustained by that responder. 

035 PPM or less averaged over an 8 hour day within that workday is a common goal of specific States Occupational Health and Safety Administration or similar state entity.  This is also a common goal of many employers despite higher regulated concentration

standards and may require the measurement of several simultaneous reference locations.

OSHA  (Occupational Health and Safety Administration)

050 PPM:  Maximum allowable concentration for a workers continuous exposure in any eight (8) hour period.  This 8-hour average requires continuous measurement and accurate reporting in the workplace.

BPI

36 to 99 PPM is excessive.  Medical alert.  Conditions must be mitigated.  Ventilation required.  Always test garage space.  Individually test combustion appliances.  All repair is to be conducted by a qualified technician with proper test equipment.

BPI

100 to 200 PPM is dangerous (and is a common building evacuation standard.)  Medical alert conditions.  Suggested occupant health inquiry.  Advise that someone else drive them to seek medical help; 15 minute maximum exposure upon discovery.  Report incident to Authority of Jurisdiction.

200+ PPM is extremely dangerous.  Universally accepted as an evacuation action level. The health of occupants should be monitored, emergency conditions exist.  Building should be ventilated and searched for additional occupants.  Combustion systems should be thoroughly tested for CO production and dispersion.  Report incident to an Authority of Jurisdiction.

Any increase in PPM from outside to inside warrants further source investigation and is documented, reported and even fixed is common in jurisdictions where a fuel supplier also is considered an Authority of Jurisdiction.  This standard is also common to some federally and state funded weatherization programs as well as protocol to  some private companies engaged in carbon monoxide testing.

Carbon monoxide measurements in flue gases also must meet specific concentration standards.  Though CO concentration standards have existed for appliances and other combustion systems for many years, lack of testing and misunderstanding of CO measurement has occurred.

As stated earlier, carbon monoxide can be measured in flue gases as CO PPM or CO PPM Air-free.  Appliance manufacturers must produce units that comply with measurements of CO Air-free that are less than the listed maximums.

The following CO PPM Air-free measurements are offered along with common CO PPM standards found in jurisdictions where single sensor CO instruments are used. 

ANSI Z21   (American National Standards Institute)

200 PPM CO Air-free is the maximum concentration

from an unvented space heater.

ANSI Z21 and EPA

400 PPM CO Air-free is the maximum allowed in furnace flue gas.

ANSI Z21

800 PPM CO Air-free is the maximum allowed for gas oven emissions.

To many technicians who have been and are performing combustion gas tests regularly, these concentrations are extremely high in reference to CO levels that can be expected from combustion systems finely tuned and maintained.

Additionally, CO Air-free measurement is not always performed due to lack of understanding about the requirement and lack of technicians’ understanding about the importance of O₂ measurement in establishing the efficiency and safety parameters of combustion systems.

This manual has discussed air measurement standards for CO in ambient air and flue gas standards for CO Air free.  Monitoring flue gas readings commonly occur throughout North America.

The most criticism about flue gas testing often times comes from technicians or companies that do not test.  Some of the most common arguments against testing include:

·        “If I test, I become liable.” and

·         “The instruments cost too much to buy and maintain.”

Fortunately, many technicians and companies regularly test flue gases on furnaces, water heaters, ovens, boilers and other systems.  They are aware that liability begins as soon as they walk in the door and that testing generates more business.

Carbon monoxide problems can be identified and minimized.

It is common to find technicians, gas utility company personnel and others who do not understand the CO Air Free measurement and who often mix Air Free and non-Air Free measurement numbers.

Many technicians and inspectors utilize single gas CO test instruments (like the Bacharach Monoxor II).  The action levels they use for how much CO is too much in flue gases is reported in CO PPM not CO PPM air free because the excess air in that flue gas sample has not been calculated out of the reading.

The CO in PPM will be a significantly lower number than the CO Air Free measurement ceiling offered by ANSI, EPA or AGA.

However, knowing that an atmospheric natural gas system’s flue gases, for example, generally contains 7 to 9% O₂ and utilizing our CO Air Free formula, we would calculate the furnace ceiling amount of 400 PPM CO Air Free to be equivalent to around 225 PPM CO or higher when using single gas instrument.