Small doesn’t necessarily mean safe. Low-horsepower gasoline engines like those used on pressure washers, portable waterjetters, air compressors, and generators produce carbon monoxide in exhaust just as larger engines do. When used for work indoors or in semi-enclosed spaces, they need to be treated with care.

“Carbon monoxide (CO) can rapidly accumulate even in areas that appear to be well ventilated and build up to dangerous or fatal concentrations within minutes,” according to a fact sheet from the National Institute for Occupational Safety and Health. If you doubt it, consider these examples cited by NIOSH:

A plumber used a gasoline-powered concrete saw in a basement with open doors and windows and a cooling fan. He got a severe headache, dizziness and other symptoms related to CO poisoning.

A farmer died of CO poisoning while using a pressure washer with an 11 hp engine to clean his barn. He had worked 30 minutes before being overcome.

A worker at a water treatment plant lost consciousness working in a large room with an 8 hp gasoline-powered pump. Doors next to the work area were open. His hospital diagnosis was CO poisoning.

Five workers were treated for CO poisoning after using two 8 hp pressure washers in a poorly ventilated parking garage.

These examples show a range of CO effects in varied settings, with exposures lasting different amounts of time and with different types of ventilation. Even opening doors and windows and using fans did not ensure safety. CO is a dangerous poison, and operating gasoline engines and tools indoors is risky.

Small gasoline engines and tools produce high concentrations of CO – a poisonous gas that can cause illness, permanent nervous system damage and death. Because it is colorless, odorless, and nonirritating, CO can overcome a person without warning. People can quickly show symptoms that inhibit their ability to seek safety.

Many workers gain a false sense of security because they are familiar with small engines, having used them many times before. To prevent CO poisoning, NIOSH offers several recommendations for employers and equipment users.

Don’t allow use of tools powered by gasoline engines inside buildings or in partially enclosed areas unless the engine can be located outside, away from air intakes. For example, always place the pump and power unit of a pressure washer outside and run only the high-pressure wash line inside.

Consider using tools powered by electricity or compressed air for indoor jobs where practical and where it is safe to do so.

Learn the symptoms of CO overexposure: headache, nausea, weakness, dizziness, visual disturbances, changes in personality, loss of consciousness. Any of these can occur within minutes. Watch co-workers for symptoms.

If you have any symptoms, immediately turn off equipment and go outdoors or to a place with uncontaminated air.

Call 911 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.

Use personal CO monitors where potential sources of CO exist. Monitors should have audible alarms to warn workers when CO levels are high.

In addition, employers should conduct workplace surveys to identify potential sources of CO exposure, and educate workers about the sources of CO and conditions that may result in CO poisoning.

Don’t let a small and inexpensive work tool become the cause of an incident that costs you dearly – most of all through the loss of a valued employee.