Ignition temperature, ambient temperature and temperature classification are several common basic concepts in explosion-proof certification.

Ignition temperature refers to the minimum temperature at which flammable gases and vapors in an explosive atmosphere are ignited.

Ambient temperature group refers to the operating temperature range of equipment used in explosive atmospheres. In accordance with the standard GB/T 3836, this range is typically -20°C to +40°C. No additional ambient temperature marking is required in this case. However, if the equipment is expected to be used in an environment outside this temperature range, it is considered a special case. The marking shall include the ambient temperature range specified by Tₐ (or Tₐₘᵦ) with the upper and lower limits. If this is not feasible, the marking shall comply with the symbol "X" and specify the special operating conditions including the upper and lower ambient temperature limits.

Temperature classification refers to the maximum surface temperature of explosion-proof equipment used in explosive atmospheres, which is typically divided into T1 to T6 groups.

Table 1 Relationship between ignition temperature of gases or vapors and equipment temperature classification groups