How clean is shop air?

The focus has been on the impact of truck emissions on the environment. But maybe it's time we gave some more thought to exhaust in our shops.Over the years we've visited a few truck shops that, beyond rolling up the doors and opening the windows, had absolutely no extraction system for exhaust fumes. The heavy deposits of exhaust soot staining the ceilings above the work bays made them easy to identify.But

The focus has been on the impact of truck emissions on the environment. But maybe it's time we gave some more thought to exhaust in our shops.

Over the years we've visited a few truck shops that, beyond rolling up the doors and opening the windows, had absolutely no extraction system for exhaust fumes. The heavy deposits of exhaust soot staining the ceilings above the work bays made them easy to identify.

But while these extreme situations are in the minority, inadequate ventilation is a fact of life in a great many more facilities. The quality of the air inside a shop can deteriorate for many reasons, from faulty fan motors to ductwork that is punctured, damaged, or undersized. Sometimes the handy collection devices that fit over the tops of exhaust stacks do not stay in place during all test procedures, or a shop does not possess a full selection of tailpipe adapters so the systems can't be properly used on all vehicles.

There are times when truck engines must be operated indoors at full or partial load, such as when A/C systems are being serviced or dynamometer evaluations are made. In a busy 20-bay shop, one can figure that a truck engine will be running indoors at least 30% of the time.

Unfortunately, many shop managers do not fully appreciate the health hazards associated with running diesel engines in facilities that aren't properly ventilated. When present in sufficient quantity, exhaust fumes, particulates, and gases are dangerous. The degree of the danger depends on three factors: chemical composition of the fumes, or particulate matter; concentration of pollutants in each technician's breathing zone; and the length of exposure to the gases and fumes.

At the very least, technicians who toil in poorly ventilated facilities are likely to suffer from the teary-eye, sore-throat, burning-nostril syndrome. These, however, are the least injurious reactions to the chemicals present in diesel exhaust. Some of the most noxious components include carcinogens such as formaldehyde, acetaldehyde, and 1-3 butadiene, meaning prolonged exposure can lead to cancer. Another dangerous compound in diesel exhaust, carbon monoxide (CO), has been labeled the number one cause of accidental poisoning deaths in the nation by the Journal of the American Medical Assn.

The Occupational Safety and Health Administration is so concerned about carbon monoxide poisoning -- which occurs when the colorless, odorless gas prevents the blood from carrying sufficient oxygen to organs and tissues -- that it has established a maximum exposure level: 35 ppm over an 8-hour period in the general workplace.

The limit was set low because CO is so treacherous. Exposure to small amounts can impair work capacity and manual dexterity, diminishing a technician's ability to perform complex tasks. In higher concentrations, CO can cause illness, permanent neurological damage, or even death.

The first step in protecting a shop work environment from the effects of diesel smoke is to gather information about the engines and operating conditions in the facility.

Very simply, if a vehicle exhausts more than the system can handle, an indoor health hazard is created. The most direct way to conduct an analysis is to make a list of engine displacements in cubic inches or liters. Then, establish the maximum rpm at which the engines are tested in the facility and determine whether the vehicles are tested under load. Mechanical ventilation must be sized to evacuate more air than the exhaust produced.

If you have any questions about how to do this, or about system requirements, it's a good idea to have an engineer or vehicle exhaust system expert verify the correct exhaust requirements, as well as determine duct and fan sizing.

Whenever engines are run inside buildings, the health and safety of technicians, office personnel, and other unsuspecting individuals are a primary concern of insurance companies, local fire departments, OSHA representatives, and unions. Compliance with the regulations is not negotiable.

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