The effectiveness of a downdraft ventilation table to control levels of formaldehyde (50000) exposure at the morgue of a Canadian hospital was discussed. Most morgues and embalming rooms use conventional dilution ventilation systems with wall or ceiling exhaust fans. The model DEM autopsy table made by Jewett Refrigeration Company was divided into two main areas: the pedestal base and drainboard. The table was modified to have a 800 cubic foot/minute exhaust flow rate. The outside diameter of the exhaust flow line was 15.2 centimeters (cm). The central table exhaust was covered with a removable strainer to capture debris that falls off the drainboard. The table exhausted 40 to 50% of the room air supply. The remainder was exhausted through a slot exhaust at the head of the work bench. The tracer gas sulfur-hexafluoride was used to determine gas removal from the worker's breathing zone. The gas was released at key points along the table. Airborne formaldehyde was also measured during an actual embalming. No tracer gas was detected in the worker's breathing zone when released at table height and 10cm above the table top, with downward velocities of 725 and 1,000 feet/minute (ft/min) recorded. Tracer gas was detected when released at the level of the worker's nose, and downward velocity was 60 to 90ft/min. When a body was being embalmed, workers experienced 0.15 parts per million (ppm) formaldehyde, which was within current standards. The author concludes that the downward draft table can be modified to reduce exposure to formaldehyde to 0.3ppm by, for instance, placing air vents directly above the table, boosting fan size, and removing debris that accumulates in the strainer.
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