Thirty seven incidents of exploding lead acid batteries at coal mines, metalliferous mines, and quarries have been reported to the Mines Inspectorate over the last 11 years - an incidence rate of 3.4 per year for mining and quarrying operations. These batteries, used in stationary and mobile plant and vehicles, have exploded, with casings shatterin. Battery explosion incident reports show that in mobile plant and vehicle applications, VRLA batteries explode significantly less than vented batteries. For stationary plant, incidents are reported for both types of batteries. For stationary plant on standby (e.g. fire pumps) it is perceived that the incidence rate increases significantly if the cha. This bulletin cannot account for all possible battery applications, but if a battery application is about to be introduced or changed, a proper management process, taking into account the particular circumstances and the latest relevant technical information, needs to be undertaken. The risk of injury due to a battery explosion can be reduced by: 1. 5.1. MechanismH2 and O2 gases are produced inside the battery casing during charging, and when almost fully charged, the H2 and O2production rate increases. It also increases during overcharging or too rapid charging. The 2:1 volume ratio for the H2:O2produced, excluding the effect of other gases that may be present, creates a very explosive mixture. The 4% lower and 75% upper explosion limits for hydrogen in air means it can explode over a wide range of concentrations, so partial dilution/ventilation is p. 5.2. External ignitionAny ignition source in the zone where hydrogen is within its explosive range increases the likelihood of an external explosion. If a path to inside the battery exists - e.g. for a vented battery, the flame front may continue into the casing, igniting any gases there, and increasing pressure inside the casing. The casing, not designed to withstand this pressure, will probably explode, potentially injuring bystanders. For a VRLA battery, an external flame can't enter the sealed battery casing,. 5.3. Internal ignition.
