Workplace Carbon Monoxide Hazards

Overview

Carbon monoxide (CO) is a colorless, odorless, and toxic gas, which can be produced by incomplete combustion of carbon-containing materials. CO poisoning can occur from a variety of sources at work and include operating:

• Portable generators
• Small gasoline engines and tools
• Marine engines
• Pressure washers
• Forklifts
• Coal burning power plants

CO is hazardous, especially inside buildings or semi-enclosed spaces. CO can rapidly accumulate, even in areas that appear to be well ventilated, and build up to dangerous or fatal concentrations within minutes.

How it works

Many workplace tasks can result in CO exposure. Using portable generators, marine engines, small gasoline-powered engines, and other tools can be serious health hazards because they produce high concentrations of CO.

Because it is colorless, odorless, and nonirritating, people can be exposed to CO without warning. Often there is little time before they experience symptoms that inhibit their ability to seek safety.

When workers frequently use the same equipment without incident, they sometimes develop a false sense of safety. Workers in these scenarios have been poisoned on subsequent occasions.

Understanding how to prevent CO poisoning is important for employers, equipment users, tool rental agencies, and tool manufacturers.

Risks

All CO poisonings are preventable

Here is what you can do to prevent CO poisoning:

• Know the symptoms of CO poisoning:
  • Headache
  • Confusion
  • Fatigue
  • Seizures
  • Dizziness or loss of consciousness
  • Nausea
• Get to fresh air and seek medical help immediately if you, an employee, or coworker has these symptoms
• Install and frequently test a battery-operated CO detector
• Schedule regular engine and exhaust system maintenance inspections by experienced and trained technicians
• Be aware that dangerous concentrations of CO can accumulate within seconds

Recommendations

To reduce CO poisonings, employers and equipment users can:

Avoid using gasoline-powered tools inside: Avoid operating gasoline-powered engines or tools inside buildings or in partially enclosed areas. Using gasoline-powered tools indoors where CO from the engine can rapidly accumulate and can be fatal.

Place pump/power unit away from air intakes: Always place the pump and power unit of high-pressure washers, gasoline-powered air compressors or portable generators outside and away from air intakes so that engine exhaust is not drawn indoors where the work is being done. Run only the high-pressure wash line inside.

Consider using electric or compressed air-powered tools if they are available and can be used safely.

Test air regularly in areas where CO may be present, including confined spaces.

Use personal CO monitors where potential sources of CO exist. These monitors should be equipped with audible alarms to warn workers when CO concentrations are too high or when exceeding the NIOSH Ceiling limit for CO of 200 parts per million.

How to get started

Employers can:

• Conduct a workplace survey to identify all potential sources of CO exposure and measure air concentrations
• Consider using equipment powered by electricity, batteries or compressed air, if they can be used safely
• Place gasoline powered engines outside and at least 20 feet from any building openings (windows, doors, garages, etc.)
• Regularly monitor employee CO exposures to determine the extent of the hazard
• Educate workers about the sources and conditions that may result in CO poisoning as well as the symptoms and ways to reduce CO exposure

Equipment users can:

• Learn to recognize the warning symptoms of CO poisoning
• If you have any symptoms, immediately turn off equipment and go outdoors or to a place with uncontaminated air
• Call 911 or another local emergency number for medical attention or assistance if symptoms occur
  • Do not drive a motor vehicle–get someone else to drive you to a health care facility
• Stay away from the work area until the tool has been deactivated and measured CO concentrations are below accepted guidelines and standards
• Watch coworkers for the signs of CO toxicity

Story from the field

In August 2000, the National Park Service, through the Department of the Interior, requested assistance from the National Institute for Occupational Safety and Health (NIOSH) and the U.S. Coast Guard to evaluate visitor and employee carbon monoxide (CO) exposures from generators and propulsion engines on houseboats following the deaths of two boys from CO poisoning. This initial investigation characterized CO poisonings through epidemiologic data gathering and the measurement of severely hazardous CO concentrations on houseboats at Lake Powell. Since that initial investigation, over 800 boating-related poisonings in 35 states were identified with over 140 of these poisonings resulting in death. Over 300 of the poisonings occurred on houseboats, with more than 200 of these poisonings attributed to generator exhaust alone.

The investigations showed that extremely hazardous CO concentrations could accumulate beneath or near the rear deck of the boat where generators exhausted. CO concentrations in this area were well above the NIOSH Immediately Dangerous to Life and Health (IDLH) value of 1,200 parts per million. One of the major obstacles to safe use of boat generators was a lack of emission (engineering) controls. NIOSH researchers began partnering with boat builders and marine engine manufacturers in 2001 to address the issue of CO poisonings from marine generators. Work in this area resulted in new low-emission generators and other engine technology which has greatly reduced the risk of CO poisoning in the marine environment. Two major manufacturers of marine power generation systems developed low-CO emission generators. NIOSH evaluations subsequently showed that the addition of technologies such as catalytic converters and electronic fuel injection to marine generators has helped to dramatically reduce CO emissions by 99%.1

As of 2009, U.S. generator and marine engine manufacturers have been manufacturing commercially available cleaner burning engines that dramatically reduce CO emissions. This has been codified through Environmental Protection Agency (EPA) regulations. The California Air Resources Board (CARB) also acted to implement CO requirements. In addition, the U.S. National Park Service has issued new requirements for concession boat rental and marina operations to prevent CO poisoning. Several major houseboat rental companies have retrofitted their entire fleet with control systems. Read a 2014 summary of the research.

Following this research, two new voluntary CO safety standards were developed for portable generators:2

• NSI/PGMA G300-2018, Safety and Performance of Portable Generators
• ANSI/UL 2201-2018, Carbon Monoxide (CO) Emission Rate of Portable Generators.

Both standards prescribe the use of onboard CO sensors with automatic shutoff at air concentrations above a set limit. In addition, the UL 2201 standard also requires reduced emissions of CO in portable generator exhaust. The Consumer Products Safety Commission conducted an analysis of these standards and found that that generators compliant with the UL 2201 standard would avert nearly 100 percent of the deaths and PGMA G300 standard would avert nearly 87 percent of those deaths that occurred with the current, non-compliant generators.

Publications

Featured publications

Publication search

Search the NIOSHTIC-2 database of occupational safety and health publications funded in whole or in part by NIOSH. The following links provide customized NIOSHTIC-2 search results for CO hazards and related topics:

• Carbon monoxide and engines or generators
• Health Hazard Evaluations on carbon monoxide

NIOSH FACE reports

Resources and tools

External resources