The valve contains a pressure-sensitive element (often a diaphragm, spring-loaded plate, or fusible material) that monitors internal battery pressure. During normal operation, the valve remains sealed to prevent electrolyte leakage and external contamination.

If a battery experiences overcharging, thermal runaway, or internal short-circuiting, chemical reactions generate gases (e.g., H₂, CO, and organic vapors), causing pressure to rise. When pressure exceeds a pre-set threshold (typically 0.5–2 bar for lithium-ion batteries), the sensitive element deforms or melts, triggering the valve to open.

Once activated, the valve opens a passageway for gas to escape safely. The design ensures gradual pressure relief to avoid sudden decompression, which could ignite gases.

Some valves use multi-stage vents: initial small openings release gas slowly, and larger ports open if pressure continues to rise. This controlled release prevents pressure buildup that could rupture the battery casing, a common cause of explosions.

Advanced valves integrate flame arrestors (e.g., mesh screens or porous materials) to quench sparks and prevent external flames from entering the battery.

For reusable valves, a pressure-sensitive membrane or spring mechanism reseals the valve after pressure drops, preventing electrolyte spillage and maintaining battery integrity. Disposable valves, however, remain open post-activation but are designed to prevent debris from entering the battery.

Modern explosion proof valves often work with BMS, which monitor voltage, temperature, and pressure in real time. If BMS detects abnormal conditions, it can pre-emptively trigger the valve or adjust charging parameters to reduce pressure, enhancing safety.

This integration ensures both reactive and proactive explosion prevention.

Valves are typically made of heat-resistant materials (e.g., stainless steel, PEEK) to withstand high temperatures during thermal runaway.

Their structure balances durability with sensitivity: robust enough to resist mechanical impacts but responsive to subtle pressure changes. For example, lithium-ion battery valves may use a thin metal diaphragm that ruptures at a precise pressure, while flow channels are optimized to minimize pressure drop during normal operation.