Lead-Acid Storage BatteriesDOE-HDBK-1084-95MAINTENANCEa. Rate of gas Formation is from Linden, 1984 (Handbook of Batteries and Fuel Cells).Rev. 0Page 35Batteriesthoroughly with clean water if acid gets into the eyes, skin, or clothing and obtain medicalattention when eyes are affected. A bicarbonate of soda solution is commonly used toneutralize any acid accidentally spilled. After neutralization the area should be rinsed withclear water.Precautions must be routinely practiced to prevent explosions from ignition of the flammablegas mixture of hydrogen and oxygen formed during overcharge of lead-acid cells. Themaximum rate of formation is 0.42 L of hydrogen and 0.21 L of oxygen per ampere-houraovercharge at standard temperature and pressure. The gas mixture is explosive whenhydrogen in air exceeds 4% by volume. A standard practice is to set warning devices to ringalarms at 20 to 25% of this lower explosive limit (LEL). Hydrogen detectors are availablecommercially for this purpose.With good air circulation around a battery, hydrogen accumulation is normally not aproblem. However, if relatively large batteries are confined in small rooms, exhaust fansshould be installed to vent the room constantly or to be turned on automatically whenhydrogen accumulation exceeds 20% of the lower explosive limit. Battery boxes should alsobe vented to the atmosphere. Sparks or flame can ignite these hydrogen mixtures above theLEL. To prevent ignition, electrical sources of arcs, sparks, or flame should be mounted inexplosion-proof metal boxes. Flooded batteries can similarly be equipped with flamearrestors in the vents to prevent outside sparks from igniting explosive gases inside the cellcases. It is mandatory to refrain from smoking, using open flames, or creating sparks in thevicinity of the battery. A considerable number of the reported explosions of batteries comefrom uncontrolled charging in non-automotive applications. Often batteries will be charged,off the vehicle, for long periods of time with an unregulated charger. In spite of the fact thatthe charge currents can be low, considerable volumes of gas can accumulate. When thebattery is then moved, this gas vents, and if a spark is present, explosions have been knownto occur. The introduction of calcium alloy grids has minimized this problem, but thepossibility of explosion is still present.Some types of batteries can release small quantities of the toxic gases, stibine and arsine. These batteries have positive or negative plates that contain small quantities of the metalsantimony and arsenic in the grid alloy to harden the grid and to reduce the rate of corrosionof the grid during cycling. Arsine (AsH ) and stibine (SbH ) are formed when the arsenic or3 3antimony alloy material comes into contact with hydrogen, generated during overcharge ofthe battery. They are extremely dangerous and can cause serious illness and death. Ventilation of the battery area is very important. Indications are that ventilation designed tomaintain hydrogen below 20% LEL (approximately 1% hydrogen) will also maintain stibineand arsine below their toxic limits.The following summary of safety precautions as found in DOE-STD-3003-94, Backup PowerSources for DOE Facilities, will aid in preventing personal injury and damage to facilities:
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