Lead acid batteries can cause serious injury if not handled correctly. They are capable of delivering an electric charge at a very high rate. Gases released when batteries are charging – hydrogen (very flammable and easily ignited) and oxygen (supports combustion) – can result in an explosion.
Overall, the National Fire Protection Association says that lead-acid batteries present a low fire hazard. Furthermore, the NFPA reports that (based on limited information) flooded lead-acid batteries are less prone to thermal runaways than valve-regulated lead-acid batteries (VRLA).
Lead-acid batteries must be carefully handled and stored as per their SDS. Hazards associated with lead-acid batteries include: Lead-acid batteries are recognised as a Class 8 Corrosive. However, the legal obligation for spill containment depends on if the lead-acid battery is closed (sealed).
Inorganic lead dust is the primary hazard in the battery manufacturing industry. Lead is a non-biodegradable, toxic heavy metal with no physiological benefit to humans. Battery manufacturing workers, construction workers, and metal miners are at the highest risk of exposure.
Battery acid itself is not flammable. But the hydrogen gases that it emits during charging are flammable and highly explosive at high concentrations. Can Battery Acid Start a Fire? Yes, lead-acid battery fires are possible – though not because of the battery acid itself.
In a vented lead-acid battery, these gases escape the battery case and relieve excessive pressure. But when there’s no vent, these gasses build up and concentrate in the battery case. Since hydrogen is highly explosive, there’s a fire and explosion risk if it builds up to dangerous levels. What Is a Dangerous Level?