Special Topics in Safety Management

Caution! Forklift Exhaust Gases Can Kill

It’s well known that moving forklifts can kill, but so can those standing still … if their gas-powered engines are left idling. The problem: carbon monoxide poisoning.  Here are some solutions.

The 75 employees of an Iowa plastics plant came to work as usual one August day, never knowing what lay in store for them.

As they labored at their tasks, some began to feel headachy, others sick in other ways.  By the end of the 3rd shift, nearly half the workforce shared the misery. Ten employees were ill enough to be taken to the hospital.


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What befell them? Not some mystery germ or criminal plot.

In fact, the culprit was the plant’s two innocent-appearing forklift trucks, shuttling about their normal rounds. When investigators checked their propane-powered propulsion systems, they found some 40,000 parts per million (PPM) of odorless, tasteless, colorless carbon monoxide (CO) gas spewing from their exhaust pipes. The safe guideline for CO emissions is as little as 1/20th  of that amount.

Forklifts are useful industrial devices, but their safety hazards are well known. Some 100 workers are killed each year in forklift accidents, and 20,000 are injured.

Most of this carnage comes from trucks overturning or loads getting loose and crushing drivers and bystanders. But carbon monoxide poisoning from propane, gasoline, or LPG-powered lift trucks can be just as deadly. So much so that Occupational Health & Safety, as well as other sources, recently published extensive articles on the subject.

The danger exists when gas-powered trucks are used in enclosed, or even partially enclosed spaces. All fuel-burning engines produce some CO, but in road vehicles, complex pollution control systems convert much of it into far less harmful substances.

Most forklift trucks have no similar systems. The responsibility for reducing the hazard, therefore, falls to the operator.  Here’s how experts recommend doing it:

  • Avoid using the truck indoors. That applies to both completely enclosed spaces, such as factory buildings or warehouses, or partially covered spaces, such as supply sheds. CO builds up fast, and there’s no way to know it’s there without a test meter … until you feel the effects, that is. Some experts feel that the safest material mover for indoor use is an electric powered truck. Batteries pose their own risks, but CO poisoning is not one of them.
  • If the truck must be used indoors, provide adequate ventilation. The American Conference of Governmental Industrial Hygienists (ACGIH) recommends a dilution rate of 10,000 cfm for a propane truck, or 16,000 cfm for a gas-powered unit, reports OH&S.
  • Avoid idling, even outdoors, and especially near windows or vent openings where exhaust gas can be sucked into occupied spaces.  In fact, the truck really should be shut down except when it’s actually being used… a practice that also saves fuel.
  • Keep the engine in tune. Well-maintained engines burn fuel more efficiently, reducing the CO released into the exhaust. The drop in CO from a simple tune-up, (adjusting the carburetor, cleaning air filters, checking timing), can be dramatic. CO emissions can skyrocket from a normal 4/10ths of a percent of exhaust gas to 5 or even 10 percent simply because the engine is improperly maintained. Fuel use goes up, too. Some experts recommend that engine tune be checked every 250 hours of use.

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  • Add a catalytic converter. This is the system modern cars use to greatly neutralize emissions. Aftermarket manufacturers offer units that are direct replacements for the original parts with claims that emissions can be cut as much as 99 percent. Other systems, such as closed-loop carburetion, can improve matters further.
  • Think about converting to compressed natural gas. CNG is less polluting than LPG or propane. One downside: You need a special filling apparatus to refuel.
  • Test your exhaust. This is done with a CO analyzer. Some experts suggest a test every day the truck is used.
  • Consider a new truck. They have far more efficient engines, right out of the box.

    One final bit of advice: Train your employees on the signs and symptoms of CO poisoning, and what to do if they think it’s happening.  We’ll delve into that tomorrow.

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