Did You Know Carbon Monoxide Sensors Do Not Detect Diesel Exhaust?
Popular uses of carbon monoxide sensors in the building automation industry involve monitoring vehicle exhaust. Sensors are commonly installed in parking garages to monitor carbon monoxide levels and provide an input signal for a ventilation control system or building automation system. This system then controls the ventilation by opening dampers and controlling fans to maintain acceptable carbon monoxide levels. Sensors are also utilized to prevent introducing carbon monoxide into the building when the outside air intake is located in an area where exhaust fumes may be present, such as near loading docks. In this application, the presence of carbon monoxide will cause the outside air dampers to close and remain closed until the outside air is free of fumes. Kele now offers two products that may be used in these applications. The WCO-1B Carbon Monoxide Sensor provides a 4-20 mA output over 0-200 ppm. The new GMT-CO Series Gas Monitor/Transmitter is also available for sensing carbon monoxide and includes a 4-20 mA output over 0-250 ppm, and an alarm relay factory set at 35 ppm. Table 1 shows exposure levels recommended by several agencies.
What if the vehicles in the parking garages or at the loading docks are not gasoline powered, but are diesel engines? Many people are surprised to learn that carbon monoxide sensors will not detect diesel exhaust. Although carbon monoxide is one of the components of diesel exhaust, the levels are much lower than from a gasoline engine and therefore difficult to detect. Since a diesel engine emits a lower level of carbon monoxide, is it necessary to monitor for diesel exhaust fumes? The United States Department of Labor states, “Over one million workers exposed to diesel exhaust face the risk of adverse health effects ranging from headaches to nausea to cancer and respiratory disease”. (1)
Although OSHA recognizes the potential hazards of diesel exhaust, there are no current regulations in place for monitoring it. They state, “There are standards for various chemical components of diesel exhaust. However, there are currently no standards for diesel exhaust as a unique hazard.” (1) How should you monitor for diesel exhaust? A good way to detect diesel exhaust is by monitoring one of its primary components – nitrogen dioxide. This may be accomplished by using a GMT-NO2 Gas Monitor/Transmitter. The GMT-NO2 provides a 4-20 mA output over 0-10 ppm of nitrogen dioxide with an alarm relay factory set at one ppm. While carbon monoxide is very slightly lighter than air and carbon monoxide sensors should be installed 3-5 feet above the floor, nitrogen dioxide is much heavier than air and nitrogen dioxide sensors should be installed 1 to 2 feet above the floor. Table 1 shows exposure levels recommended by several agencies.
The “point lists” for building automation systems include an increasing number of unique applications. The new GMT Series Gas Monitor/Transmitter, in addition to carbon monoxide and nitrogen dioxide, is available to monitor hydrogen (battery rooms), ammonia (refrigerated warehouses, mechanical rooms, and arenas), chlorine (swimming pools), combustibles (boiler rooms), and other gases. As your business expands into new markets, Kele is dedicated to providing the interface devices to help you obtain these projects.
(1) http://www.osha.gov
- OSHA – Occupational Safety and Health Administration (U.S. Dept. of Labor)
- ACGIH – American Conference of Governmental Industrial Hygienists
- NIOSH – National Institute for Occpational Safety and Health (U.S. Dept of Health and Human Services)
- TWA – Time Weighted Average – Example calculation of 8 hour TWA: Assume 2 hours exposure at 75 ppm, 2 hour exposure at 45 ppm, 4 hours exposure at 20 ppm.
- STEL – Short Term Exposure Limit.
