By: Thomas H. Welby Published: August 2017

Carbon Monoxide Poisoning as a Construction Hazard

Most people are aware that carbon monoxide (CO) gas is a colorless gas with no taste or smell, and, when inhaled, inhibits the blood in bringing oxygen to cells, tissues and organs.  We have all heard accounts of people being overcome and dying from carbon monoxide poisoning, and many of us have carbon monoxide detectors or alarm systems in our homes.

Carbon monoxide is a common hazard, resulting from the incomplete combustion of natural gas and any other material containing carbon, such as gasoline, kerosene, oil, propane, coal, or wood.  CO exposure at high levels can result in death, or permanent organic injury, in a matter of minutes.  Since construction operations often involve gasoline-powered or other fuel-burning equipment, and work indoors (or in poorly-ventilated outdoor spaces) it’s a construction hazard, with welders and forklift operators at particularly high risk.

Situations in which carbon monoxide can pose a serious hazard in construction include the use of equipment powered by gasoline or by liquefied petroleum gas (propane and/or butane), such as generators or cut-off saws, in enclosed spaces — indoors, certainly, but also in trenches, or outdoor spaces where plastic sheeting is in place to protect against dust, rain, etc.  CO tends to build up in pockets in poorly-ventilated areas.

CO gas may be a hazard, also, where building renovations disturb gas flues or ventilation systems, or where gas-powered stoves, fireplaces or other appliances are incorrectly installed.

All fuel-burning equipment emits some quantity of carbon monoxide.  This includes car, truck and forklift engines, gasoline-powered power washers, construction equipment powered by gasoline or propane, and non-electric heaters.  Any fuel-burning equipment to be used indoors, or in semi-enclosed outdoor spaces, must be maintained and tuned regularly, as a poorly-tuned gasoline engine can produce up to 12 times as much CO as a well-tuned one.  (Water heaters, space heaters, and cooking ranges that produce CO should also be maintained in good working order, to reduce CO formation.)

Indications that incomplete combustion is occurring, and that CO may be produced, include yellow or orange rather than blue flames, soot or yellow/brown staining around or on appliances, pilot lights that frequently blow out, and increased condensation inside windows.

Keeping gasoline-powered equipment well-tuned, however, is not sufficient, where such equipment is to be used indoors, or in confined or semi-enclosed spaces (such as a garage, crawl space, or basement).  Generators should never be operated indoors — and, when operated outdoors, they should be kept away from doors, windows or vents, which could allow CO to enter the structure, and build up in occupied spaces.  The generator should also be placed with at least 3 to 4 feet on all sides and above it, to ensure adequate ventilation.

Optimally, fuel-burning equipment producing more CO than, say, a gas range should not be used at all in indoor or partially-enclosed spaces.  Where it is necessary to operate such equipment in such spaces, however, all areas where fuel-burning equipment is to be used must be ventilated by mechanical means to the outside air.

 Air-monitoring devices with audible alarms should be deployed wherever practicable.  OSHA’s PEL (averaged over 8 hours) for CO is 50 ppm; a maritime standard (not applicable to the construction industry) requires that employees be removed from the premises, if CO levels reach 100 ppm.  Other agencies recommend that long-term exposure not exceed 35 parts per million, and that the alarms should be set at a lower value.  (The maximum short-term exposure value for CO is 400 ppm; 1500 ppm is “immediately dangerous to life and health”).  OSHA prescribes that tests for CO concentrations are to be made by designated persons, using gas detector tube units (e.g., Drager, Gastec) certified by NIOSH under 30 CFR Part 11, or other instruments, whose accuracy is as great or greater.

Respirators with appropriate canisters may be used for short periods under certain circumstances, where CO levels are not exceedingly high.  More heavy-duty equipment, such as a full-facepiece, pressure-demand self-contained breathing apparatus, certified by the National Institute for Occupational Safety and Health, is indicated, where work must be performed (or rescue operations carried out) where CO concentrations in the “immediately dangerous to life and health” range are suspected.

During the planning stage, in advance of building renovations, the impact of the work on existing gas-fired systems should be carefully evaluated.  Also, future maintenance access to flue systems concealed within voids should be provided for, and properly documented.

It’s a good idea, also, to use electrical appliances in lieu of gasoline or propane-powered ones, or to locate generators, etc. outside, and in well-ventilated spaces.

As always, equipment maintenance and employee training are essential.  In addition to knowing how to implement the controls properly, employees should be taught that drowsiness, faintness, headache, breathlessness, nausea and an irregular heartbeat are early signs of CO poisoning, and that these symptoms may be confused with food poisoning, the flu or other viral infections, or fatigue.

If not properly trained concerning the dangers of carbon monoxide, workers experiencing these early signs may not know that they need to move away from the source of the CO gas, alert others, and seek immediate medical attention.  It is critical that employees be trained that they must never ignore symptoms that may be the result of carbon monoxide poisoning.  Workers should be trained, also, to alert supervisory personnel to any situation that might cause CO to accumulate.

 Workers responding to an emergency situation where CO may be present may themselves be exposed to potentially-fatal levels of CO gas, and all employees should be warned accordingly as part of their training.  Obviously, it is best if rescuers are skilled in in carrying out such operations, and in the use of recovery equipment.  They should use supplied-air or self-contained respirators in entering any area where concentrations of CO may be present.

The victim should be moved at once to an open area, and “911” or other emergency responders summoned.  If the victim is breathing, 100% oxygen should be administered, using a tight-fitting facial mask.  If the victim has stopped breathing, CPR should be administered by a trained individual.  Appropriate respirators, supplies of oxygen, etc. must be kept on hand, if your employees work in proximity to fuel-burning engines or equipment, whether the same is in use by your employees, or by other trades.

Finally, the design, installation, maintenance, alteration and inspection of fuel gas piping and equipment is governed by a variety of state and local codes.  To ensure safety, it is critical that all such work be performed in strict conformity with all applicable codes, and by persons holding appropriate licenses or permits, as may be required by state or local law.

Carbon monoxide is a formidable danger.  Because it is detectable only with special equipment, can cause serious injury or death within minutes, and can accumulate from something as easily done as the improper placement of a generator too close to windows and vents, it must be guarded against assiduously.

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