RTCA DO-160 – Section 9.0 – Explosive Atmosphere
The Explosive Atmosphere test specifies requirements and procedures for aircraft equipment that may come into contact with flammable fluids and vapors such as those specified herein.
It also refers to normal and fault conditions that could occur in areas that are or may be subjected to flammable fluids and vapors during flight operations.
The flammable test fluids, vapors or gases referred to in this section simulate those normally used in conventional aircraft and that require oxygen for combustion (e.g., mono-fuels are not included).
These standards do not relate to potentially dangerous environments occurring as a result of leakage from goods carried on the aircraft as baggage or cargo.
Category A is designed so that:
In normal operation the temperature of any surface will not rise to a level capable of causing ignition, nor will any operating part cause ignition so that it meets the non ignition test specified in paragraph 9.6.2.
Ignition of an explosive mixture is contained within the equipment without igniting an explosive atmosphere surrounding it so that it meets the Containment tests specified in paragraph 9.6.1.
Hermetically sealed equipment meeting subparagraph 9.3.1 b. shall be identified as Category A equipment.
Category E is not hermetically sealed and not contained in cases designed to prevent flame and explosion propagation. Such equipment is designed so that in operation the temperature of any internal or external surface will not rise to a level capable of causing ignition, nor will any operating internal part cause ignition so that it meets the non ignition test specified in paragraph 9.6.2.
Category H contains hot spot surfaces (external or internal) and are non-spark producing under normal operating conditions (see paragraph 4.6.1).
Such equipment designed so that in normal operation the temperature of any internal or external surfaces will not rise to a level capable of causing ignition so that it meets the components or surface temperature test of paragraph 9.6.3.
Hermetically sealed equipment meeting temperature requirement on external surface shall be identified as Category H equipment.
Explosive Atmosphere Proof
Equipment is explosion proof when it has been determined that there is negligible risk that it will cause an explosion of a flammable gas or vapor within the declared environment.