Batteries can release explosive gases, and if these gases are ignited they can explode and cause death or serious injury. Lead-acid batteries release hydrogen as they charge. Hydrogen has no colour or smell, spreads quickly, rises to the highest point of an enclosed space, and burns or explodes across a wide range from 4.1% to 74.2% by volume. Gas can also be released under abnormal conditions such as overheating. If the vented gas builds up near hot parts or another ignition source, the result can be a fire or an explosion. Powin storage manuals warn that off-gassing can create an atmosphere that is hazardous to life and may explode if the space is not properly ventilated. Ventilate battery rooms and enclosures so that hydrogen stays below 1 percent and cannot collect in pockets at the ceiling. If mechanical ventilation is used, fit airflow alarms that trigger when the fan fails. Keep flames, sparks, embers, smoking and hot plates away from batteries and gas paths. Use non-sparking tools, and touch grounded metal to discharge static before touching a battery. Install and maintain batteries as the manufacturer specifies and never heat them above their permitted temperature. Post signs that warn of the hydrogen explosion hazard.
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controlled_byc1 verified · fact Energy storage ventilation proposed
Scope: standard NFPA 70E 2009 proposed
Conditions: Batteries of the vented type; the same limit is also given for VRLA batteries
Ventilation shall be provided so as to prevent liberated hydrogen gas from exceeding 1 percent concentration.
sec=h108 h=54c337885cf9verified by: review-workflowverified on: 2026-10-24
c2 drafted · lead Ignition source control proposed
Keep open flames, embers, sparks, hot plates, smoking and other ignition sources away from batteries, gas vent paths and any place where hydrogen can collect.
sec=h58 h=859a589beb2asec=h60 h=859a589beb2asec=3.4.3 h=d5cc3a7e4bb1sec=h25 h=427d337107bdsec=h674 h=859a589beb2asec=h714 h=859a589beb2asec=h108 h=588e1edd3d68sec=h58 h=859a589beb2ac3 verified · fact Proper installation
Install, operate and maintain the battery as the manufacturer specifies. Do not heat it above its permitted temperature or burn it.
sec=h58 h=859a589beb2asec=h60 h=859a589beb2asec=h25 h=427d337107bdsec=h674 h=859a589beb2asec=h714 h=859a589beb2asec=h108 h=588e1edd3d68sec=h58 h=859a589beb2averified by: review-workflowverified on: 2026-10-24
c4 verified · fact Battery chemical hazard signage proposed
Scope: standard NFPA 70E 2009 proposed
Signs must warn of hydrogen explosion from open flame and smoking.
sec=h109 h=d6cbddb6cd6averified by: review-workflowverified on: 2026-10-24
c5 drafted · lead Non-sparking tools proposed
Scope: standard NFPA 70E 2009 proposed
Tools used on batteries must be non-sparking, with handles insulated for the maximum working voltage.
sec=h109 h=d6cbddb6cd6ac6 verified · fact Flame-arrested cell vent proposed
Scope: standard NFPA 70 (NEC) 2014 proposed
Each vented cell needs a flame arrester so that an outside spark or flame cannot ignite the gas inside the cell.
sec=h7 h=902c886728basec=h103 h=6914dda8d8c3verified by: review-workflowverified on: 2026-10-24
c7 verified · fact Ventilation airflow alarm proposed
Scope: standard NFPA 70E 2009 proposed
Where mechanical ventilation is used, airflow sensors must raise an alarm if the exhaust fan stops working.
sec=h108 h=54c337885cf9verified by: review-workflowverified on: 2026-10-24
c8 verified · fact Body static discharge proposed
Scope: standard NECA 90-2015 (Commissioning building electrical systems) proposed
Touch grounded metal first to discharge static from the body before touching batteries.
sec=3.4.3 h=d5cc3a7e4bb1verified by: review-workflowverified on: 2026-10-24review note: support check: partial - The passage states the static-discharge instruction, but it comes from a different document than the NECA 90 scope, which the passages do not show.
related_to c3related_to c8related_to c3