Be Aware of Carbon Monoxide when Using Propane-powered Equipment

A propane grinder running indoors can cause high levels of carbon monoxide.
When using propane-powered equipment indoors, contractors should take safety precautions to reduce the risk of carbon monoxide injuries. Photo courtesy of Concrete Arts

Propane-powered burnishers, grinders, trowels, saws and generators are becoming more popular with contractors looking for better results in less time. Propane equipment provides increased power, endless runtime and portability. But carbon monoxide on propane equipment can cause issues. If contractors follow proper safety procedures, however, they can effectively use this equipment indoors.

Propane, a naturally low-carbon fuel that burns very clean in internal combustion engines, produces low levels of carbon monoxide (CO). However, operators still need to be aware of the emission risks of running any engine indoors. They should practice safety precautions to reduce the risk of carbon monoxide injury on the job.

What is carbon monoxide?

CO is a colorless, odorless and toxic gas produced by incomplete combustion in engines. The Occupational Safety and Health Administration has established an eight-hour time-weighted average of 35 parts per million. It has set the ceiling of 200 parts per million as the permissible exposure limit for CO.

Common symptoms of CO exposure above the OSHA limits include headache, dizziness, weakness, upset stomach, vomiting, chest pain and confusion.

What safety precautions can I take with propane equipment on the job site?

Propane-powered equipment used to run indoors is typically calibrated to run a lean air-to-fuel ratio throughout their entire torque and power curves. This ensures the machinery produces low levels of CO. Additionally, most indoor-use propane equipment incorporates a three-way catalytic muffler. This further reduces CO’s parts per million.

Properly maintained, propane equipment should produce tailpipe CO emissions of less than 100 parts per million. This allows contractors to operate equipment below the OSHA limit in properly ventilated “big box” facilities. These include grocery stores, warehouses and construction sites.

However, poor machine maintenance, such as dirty air filters or lack of oil changes, can cause the engine to run rich. When this occurs, even propane engines can emit very high levels of CO. This can cause immediate danger to operators and those in the working area. Subsequently, contractors should follow the machine manufacturer’s daily  maintenance checklist. This includes inspecting and cleaning/replacing dirty filters if necessary.

Ventilation is critical

Ventilation, or the number of air exchanges per hour, also is critical to safely operate propane equipment indoors. OSHA has air exchange requirements that range from three to four air changes per hour in a residential facility. Those numbers increase to six to 12 in commercial buildings.

However, construction sites that don’t have HVAC installed may have no air exchange. The facility’s size and the number of air exchanges per hour combined with the exhaust flow and parts per million will determine the amount of time a propane-powered piece of equipment can be operated within the OSHA-permissible limit.

For example, a typical propane burnisher emitting 50 parts per million CO could continually operate safely in a 50,000-square-foot facility with six air exchanges per hour.

If you’re uncertain of the air exchange rate, it’s a good idea to increase ventilation by opening doors and windows. You can also create air movement with fans. Carbon monoxide is slightly less dense than air and forms a cloud in the working area. Using fans to circulate the air will increase the mixing of CO with fresh air, creating a safer environment.

It’s also important to know your working area. Propane equipment isn’t suitable for all types of indoor jobs. Small area jobs or those where windows or doors don’t open aren’t suitable for propane equipment.

What types of safety monitors are available for propane equipment?

Most propane-powered equipment today is offered with an emission monitor designed to shut down rich, high CO-producing engines. These devices read an oxygen sensor in the exhaust to determine if the engine is running lean or rich.

If the engine runs rich for a certain time, a red light will come on and the engine will shut down. While more beneficial than no monitor, these devices don’t measure the ambient air for CO emissions. It’s still possible that emissions could be higher than the OSHA-permissible limit.

Another common practice involves operators who wear handheld carbon monoxide monitors that alarm if the CO exceeds OSHA limits. While beneficial to determine high CO levels, these devices require the operator to wear them and shut down the equipment. Additionally, in case an injury renders an operator unconscious, a wearable CO monitor wouldn’t shut down the equipment.

The SAM displays the levels of carbon monoxide on propane grinders
A SAM Safe Air Monitor displays and logs both the engine air-fuel ratio and carbon monoxide level. If either reading is high, it will shut down the engine if no action is taken. Photo courtesy of Onyx Systems and Safety Technologies
Integrated monitors

Recently, many original equipment manufacturers have begun integrating carbon monoxide monitors into their equipment. These devices monitor ambient CO levels. They can shut the engine down if the CO levels are above OSHA levels.

One device, the SAM Safe Air Monitor, displays and logs both the engine air-fuel ratio and carbon monoxide level. It warns operators if either reading is high and shuts down the engine if no action is taken. It also notifies operators when engines require service. This helps to ensure high emissions don’t occur in the first place.

Propane equipment, when properly used, can save contractors time and money while producing better results. Contractors should only use propane equipment in suitable facilities with good ventilation. They should also follow daily and periodic maintenance schedules, and use available safety monitors whenever possible.

a SAM installed on a concrete grinder.
A SAM Safe Air Monitor can be integrated into a propane-powered grinder to warn operators of unhealthy CO levels. Photo courtesy of Onyx Systems and Safety Technologies

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