Switching from Liquid Propane to Electric Forklifts in the Produce Industry

In the mid-1990s, the Washington State Department of Labor & Industries (L&I) noticed an alarming trend. The state is the country's largest provider of 11 types of produce, including apples, Concord grapes, and pears. In fruit-packing warehouses across the state, workers were being exposed to dangerous — and sometimes even poisonous — levels of carbon monoxide on the job.

A major cause of this exposure turned out to be the operation of internal combustion (IC) forklifts in controlled atmosphere rooms, a mainstay of the produce handling industry. Ventilation doesn’t really work in cold rooms; they're designed to hold in cold air, which also traps the carbon monoxide released by IC engines.

Between 1994 and 1999, about 41 percent of the carbon monoxide poisonings in the state's fruit industry occurred in cold rooms or controlled atmosphere areas, reports L&I. Clearly, the industry needed to make a change.

Tracking the Causes of Carbon Monoxide Poisoning in Fruit Packing Facilities

Here's a representative case study that clearly shows the danger of operating IC forklifts in closed warehouses. This study was conducted by L&I and published in a document called "Prevent Carbon Monoxide Poisoning from Forklifts."

In June 2004, workers reported for duty at a cherry fumigation and packing facility in Washington State. A few hours later, several of them fell unconscious. Others got dizzy, nauseated, and confused.

In total, 45 employees left the warehouse in ambulances. Later analysis showed that the carbon monoxide levels in the plant reached as high as 532 parts per million in some areas. The Washington Industrial Safety and Health Act (WISHA) caps legal carbon dioxide exposure at 200 ppm.

As it turns out, staff were operating four rented forklifts in addition to their in-house fleet. The rentals hadn't been taken care of as well as the employer's trucks, and they were emitting 4-5 percent more carbon monoxide. The fruit packing company ended up paying out about $32,000 in worker's compensation as well as a $14,000 fine from WISHA.

The Transition to Emission-Free Electric Forklifts

switch from liquid propane to electric forklifts Given the prevalence of incidents like the one described above, L&I strongly recommends that employers use electric lift trucks in all enclosed facilities, especially cold rooms and controlled atmosphere areas.

Some employers worry about performance differences between their familiar IC trucks and a new electric fleet. Others are concerned about the cost. In order to waylay those fears, L&I offers the story of a 700,000 square-foot fruit packing warehouse that made the switch to electric.

Before the company replaced 35 of their 70-unit forklift fleet with electric trucks, carbon dioxide levels in the facility sometimes spiked to 90 ppm. However, WISHA uses a measurement called a Time-Weighted Average (TWA) to determine allowable exposure limits. This measurement indicates the exposure to an employee over the course of an entire shift, controlling for spikes and dips.

The official Permissible Exposure Limit (PEL) set forth by WISHA for carbon monoxide is 35 ppm with an 8-hour TWA. With IC forklifts powered by liquid propane, the facility's TWA was 50 ppm, 15 ppm over the limit.

After replacing half of their fleet with electric forklifts, the facility's carbon monoxide levels began to hover around 15 ppm over an 8-hour TWA. That's well within legal limits.

But the employer noticed other benefits, too. Electric forklifts produced just as much power as their IC counterparts. They were just as fast, but with slower acceleration, which led to fewer lift truck accidents.

Best of all, the company only spent about $300 per year on maintenance for electric trucks. They were used to spending more than three times that for their LPG fleet.

Granted, this was just one facility in one state. But their experience demonstrates the incalculable advantages of electric forklifts over IC engines in controlled atmosphere facilities around the world.


Agriculture - A Cornerstone of Washington’s Economy.” Wa.gov. Washington State Department of Agriculture, Feb. 2015. PDF. 3 Nov. 2016.

Carbon monoxide poisoning.” MayoClinic. May Clinic, n.d. Web. 3 Nov. 2016.

"Prevent Carbon Monoxide Poisoning from Forklifts." Wa.gov. Washington State Department of Labor & Industries, October 2009. Web. 3 Nov. 2016.