Carbon Monoxide in Storage Rooms and Packing Houses
Carbon monoxide is a colorless, odorless, very poisonous gas formed by the incomplete burning of fuel. It is introduced into packinghouses and storage rooms by forklifts, recirculating oxygen burners of the ARCAT or COB type, as well as some other equipment. Carbon monoxide has a relatively small molecular diameter allowing it to permeate walls, pipe joints, etc., and leak into an adjoining working environment.
The affect of carbon monoxide on humans is the result of both the concentration and the length of exposure to the gas. As the dosage is increased the response ranges from a shortness of breath to headache to possible nausea and finally to death. Table 1 summarizes the effects of carbon monoxide at various concentrations in normal air. Keep in mind that 50 ppm is a very small amount, so even small leaks could become dangerous.
The propane fuelled forklift provides most of the carbon monoxide found in fruit warehouses. Forklift drivers are most susceptible to carbon monoxide injury. There are several things which can be done to minimize the risk of injury to personnel.
Use of electric forklifts should be explored. Over a 10 year period the cost of an electric fork lift should be equal to that of a propane fork lift.
Add a catalytic converter (PTX muffler) to existing propane powered lift trucks. This will appreciably reduce emissions of carbon monoxide. An effective catalytic converter can remove 90-99% of the carbon monoxide and make the truck safer to use. Forklift engines should be allowed to reach operating temperature before being used in a confined space.
Forklifts should be properly tuned by a knowledgeable technician. Drivers should not be allowed to change adjustments on their lift trucks. The performance of lift trucks with catalytic converters should be checked with Kitagawa or MSA indicator tubes or electronic carbon monoxide detectors. Tuning should be done on a regular basis.
Forklift drivers should not work in a storage room for extended periods. For example, it is poor policy to have a single driver stacking bins which are brought into the room by other drivers. This may lead to an over exposure for the individual in the room.
Personnel protection badges are available for monitoring carbon monoxide exposure. The indicator on the badge changes color when accumulated carbon monoxide exposure approaches the danger level during an 8 hour shift. Badges must be changed regularly. (Available from Lab Safety Supply, PO Box 1368, Janesville Wisconsin 53547. 1-800-356-0783. Item B1508-7)
The work area should be well ventilated in order to reduce the rate at which carbon monoxide accumulates. Fans should be kept running in storage rooms. In rooms with plastic strip curtains, consider removing several (2 or more) flaps to improve ventilation.
Energy saving door closers and drive through curtains reduce fresh air infiltration into storage rooms by a factor of four when compared to open doors. When such energy saving methods are used the carbon monoxide concentrations are increased by a similar proportion. Workers should spend as little time as possible in these rooms and be especially aware of over-exposure. The use of carbon monoxide badges warns against over-exposure.
Carbon monoxide accumulates first at the top of the room. Be careful after suddenly turning on fans.
Gasoline powered lift trucks should never be used in storage rooms or packing areas.
Do not allow any forklift to run at idle for an extended period within a confined space.
Dr. Eugene Kupferman(1) and Henry Waelti(2)
(1)WSU Tree Fruit Research and Extension Center
1100 N. Western Ave., Wenatchee, WA 98801
(2)Extension Agricultural Engineer, Cooperative Extension, Washington State University, Pullman, WA
Post Harvest Pomology Newsletter, 2(1):14-16