Master Electrician Exam (NEC)General Electrical KnowledgeEasy
A journeyman electrician is installing a new battery backup system in a data center. The system uses lead-acid batteries. Which of the following is a critical safety concern unique to charging lead-acid batteries that requires proper ventilation?
- ARelease of toxic nitrogen oxides.
- BProduction of explosive hydrogen gas.
- CGeneration of high-frequency electromagnetic interference.
- DEmission of corrosive sulfuric acid fumes.
Show answer & explanationAnswer & explanation
Correct answer: B. Production of explosive hydrogen gas.
During charging, especially overcharging, lead-acid batteries can electrolyze water in the electrolyte, producing hydrogen gas (H₂) and oxygen gas (O₂). Hydrogen gas is highly flammable and explosive when mixed with air in certain concentrations, necessitating good ventilation to prevent accumulation.
Why the other options are wrong
- A. Incorrect. Nitrogen oxides are not typically produced during lead-acid battery charging.
- C. Incorrect. High-frequency electromagnetic interference is not a direct gaseous safety concern unique to lead-acid battery charging.
- D. Incorrect. While sulfuric acid is corrosive, the primary gaseous safety concern requiring ventilation is hydrogen, not acid fumes, although proper handling prevents acid exposure.
Lead-Acid Battery Charging Hazards
The primary hazard during lead-acid battery charging is the production of explosive hydrogen gas, which can accumulate in poorly ventilated areas and create a dangerous environment.
- Hydrogen gas is produced during electrolysis of water in electrolyte.
- Hydrogen is highly flammable and explosive.
- Requires adequate ventilation to disperse gas.
- Ignition sources must be kept away from charging areas.
Memory trick: LEAD-ACID: LOOK out for Explosions And Danger.