Purge and pressurization is a method of protection used in hazardous areas to ensure that the interior of an electrical enclosure is free of flammable gas.

Pressurization is generally used for electrical equipment that cannot be protected by other means, either because it is too large to be made explosion-proof, or too high powered to use intrinsic safety.

A vast range of electrical equipment is regularly protected by this technique, including:

• computers
• monitors
• printers
• barcode systems
• data recorders
• condition monitoring systems
• instrumentation panels
• electric motors
• analyzers
• motor control centers.

Using a suitable purge control system and pressurized enclosure, purge and pressurization not only provides an equivalent degree of safety to Flameproof (Explosion-proof) or Intrinsic Safety techniques, but also offers significant advantages of safety and durability.

The pressurization process is very simple. Purge gas, normally compressed air, keeps the internal pressure of an enclosure above the pressure outside. External flammable gas cannot enter the enclosure while it is pressurized.

Before power can be switched on, the enclosure must be purged to remove any flammable gas that may have entered the enclosure before it was pressurized. Purging is the action of replacing the air inside an enclosure with air known to be free of flammable gas.