Hazard Communication and Chemical Exposure
This domain tests whether you can get usable chemical information on a site where most of the chemicals were never labeled for you, and whether you can turn a monitoring number into an exposure decision.
The rule set
1910.1200 requires a written hazard communication program, containers labeled with GHS pictograms and signal words, accessible safety data sheets, and training before exposure. 1910.120 requires chemical hazard information and monitoring data to feed the site safety and health plan. Exposure limits come in three flavors: OSHA permissible exposure limits, NIOSH recommended exposure limits, and ACGIH threshold limit values, each expressed as an 8-hour time-weighted average, a 15-minute short-term limit, or a ceiling that must never be exceeded.
What actually injures disaster workers
Carbon monoxide from generators and pressure washers running in enclosed or partly enclosed spaces; mixing bleach with ammonia or acid and releasing chloramine or chlorine gas; silica, asbestos, and lead dust from demolishing older buildings; mold and bacteria in floodwater; unlabeled containers pulled out of debris; and secondary contamination carried home on clothing.
Worked example
Volunteers are pumping out a flooded basement while a gasoline generator runs in the adjoining crawlspace. A CO meter reads 60 ppm after four hours. The partial-shift average is 60 × 4 ÷ 8 = 30 ppm, under the 50 ppm limit - but if the reading holds for the full shift the average becomes 60 ppm, over the limit. The correct reasoning is to control the source now: shut down and relocate the generator outdoors with exhaust directed away, ventilate, re-test, and keep monitoring. Odor is not a measurement in either direction.
Traps that cost marks
"It doesn't smell, so nothing is there" and its twin, "it smells, so it must be dangerous"; stopping at the safety data sheet, which describes the product in general and not the site; assuming household products are harmless when concentrated or mixed; and forgetting that contaminated clothing is an exposure route for the family at home.