A propagation resistance (thermal propagation) test deliberately triggers thermal runaway in a single cell within a pack, typically by nail penetration or an internal heater, and monitors whether the event spreads to neighbouring cells, and what warning or containment the pack provides if it does.
The regulatory bar for this test has moved sharply in recent years. GB38031-2020 was the first mandatory standard to require only that occupants receive a 5-minute warning before a hazardous situation develops. GB38031-2025, taking effect from July 2026, raises this substantially: packs must now demonstrate no fire and no explosion for a full 2 hours after thermal runaway is triggered, with all monitored points on the pack remaining below 60℃ and no smoke entering the cabin, a considerably higher bar than any prior global standard.
See GB38031 and UN Regulation 100 for the full regulatory detail this test sits within.
Related: Pack Thermal Runaway, Thermal Propagation, Early & Passive Thermal Runaway Detection, Fire Suppression