CTA Report, Draft 1, ISP Review - US Chemical Safety and Hazard ...

8.5 Work Practices
8.5.1 Production Line Cleaning Procedures
Employees reported that production line cleaning routinely created clouds of dust. They used compressed
air, brooms, and metal tools—such as rakes, shovels, and chimney sweeps—to clean. Regular line
cleaning took place every morning. These cleaning procedures increased the suspension of combustible
dust in the production area, particularly around the line 405 oven. Over time, the procedures also
contributed to the buildup of dust on flat surfaces—thus increasing the likelihood of a fire and explosion.
Room fans were used to blow dust away from workers when they were cleaning. The fans had the
unintended consequence of increasing the dispersion of dust, which settled on elevated flat surfaces.
Before the incident, two fans were used on line 405.
NFPA and other safety guidelines warn against the use of compressed air for cleaning combustible dusts
and suggest that, whenever possible, vacuuming should be used to minimize the dispersion of dust.
8.5.2 Housekeeping
Inadequate housekeeping allowed unsafe levels of dust buildup on flat surfaces at CTA. NFPA 654
(2000) states: “[D]ust layers 1/32 inch (0.8 mm) thick on the floor can be sufficient to warrant immediate
cleaning of an area [1/32 in. (0.8 mm) is about the diameter of a paper clip wire or the thickness of the
lead in a mechanical pencil].” NFPA 654 (2000) states that a dust layer of this thickness can create a
hazardous condition if it covers more than 5 percent of the building floor area, and gives 1,000 square feet
(93 square meters) of dust layer as the upper limit for large facilities. In addition, dust accumulations on
other elevated surfaces—such as ducts, pipes, hoods, ledges, and beams, or tops of rooms and
equipment—contribute to secondary dust cloud potential and should be considered in estimating dust
loading.
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