Quicklime safety is the set of precautions for handling calcium oxide, a caustic, water-reactive material, to prevent eye, skin and lung injuries, control dust and avoid dangerous heat-releasing reactions.
Quicklime safety is the set of precautions used to protect workers who handle, store or transport quicklime (calcium oxide, CaO), a highly alkaline material that reacts with water and releases heat. It covers preventing eye, skin and respiratory injuries, controlling dust, and avoiding uncontrolled reactions with moisture.
Quicklime is made by heating limestone in a kiln and is also called burnt lime, unslaked lime or pebble lime. It is used in steelmaking, water and wastewater treatment, soil stabilization for road and building projects, construction materials, pulp and paper, mining and agriculture. When it contacts water it forms calcium hydroxide (hydrated or slaked lime) and gives off significant heat.
That combination of strong alkalinity and heat makes quicklime dangerous in ways that are easy to underestimate. Contact with sweat or tears can cause caustic burns, a splash in the eye can cause serious damage within moments, and adding water to bulk quicklime can produce enough heat to ignite nearby combustible materials.
Quicklime is a water-reactive substance. NIOSH lists water as an incompatible material because the reaction releases heat while forming calcium hydroxide. Wet storage, rain entering a bin or a hose used carelessly near a stockpile can lead to steam, spattering of hot alkaline material, and enough heat to char or ignite wood, paper or packaging. Quicklime is also incompatible with substances such as fluorine and ethanol.
OSHA's permissible exposure limit for calcium oxide is 5 mg/m3 as an 8-hour time-weighted average (29 CFR 1910.1000, Table Z-1). NIOSH recommends a lower exposure limit of 2 mg/m3, and the ACGIH threshold limit value is also 2 mg/m3. NIOSH lists the immediately dangerous to life or health (IDLH) concentration as 25 mg/m3.
A road construction crew is using quicklime to dry and stabilize wet clay soil before paving. During planning, the foreman reviews the safety data sheet and assigns a crew member to monitor wind direction so that the spreader works upwind of other workers. Crew members wear chemical goggles, gloves and long sleeves, and a portable eyewash station is set up at the staging area.
Midway through the day, a gust blows dust toward a laborer whose goggles are pushed up on his head. He gets particles in one eye and immediately goes to the eyewash station, where a coworker helps him flush for an extended period before a supervisor drives him to an urgent care clinic. The crew then holds a short meeting to reinforce wearing goggles at all times near spreading operations, and the foreman adds wind limits to the job plan.
The OSHA PEL for calcium oxide is 5 mg/m3 as an 8-hour time-weighted average. NIOSH recommends a lower limit of 2 mg/m3.
It reacts with water to form calcium hydroxide and releases heat. The reaction can cause steam, spattering of hot caustic material and, in bulk, enough heat to ignite nearby combustibles.
Quicklime is calcium oxide. Hydrated lime, or slaked lime, is calcium hydroxide, made by adding water to quicklime. Hydrated lime does not react with water in the same way but is still caustic.
Flush the eyes with clean water right away, keep flushing for an extended period and seek medical attention promptly.
Part of SafetyIQ's EHS glossary: plain-English definitions of workplace health and safety terms.
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