Purge and Pressurization: Hazardous Location Protection for Enclosures

May 21, 2015 at 1:48 pm  •  Posted in Oil and Gas  •  0 Comments

Many protection concepts can be used when placing equipment in hazardous locations. One of the easiest to understand and use is purge and pressurization, an alternative hazardous location protection concept to explosion-proof or intrinsically-safe concepts. The control system enclosure is usually rated NEMA 4 or 4X and is fitted with a means of providing a continuous flow of inert gas or instrument air which pressurizes the enclosure and presents the intrusion of explosive substances.

Purge and pressurization have several advantages over other protection methods:


  • With over 12,000 SKUs of readily available Hoffman Enclosures, you can select from a broad array of sizes of general purchase enclosures making design, assembly and commissioning faster.
  • Hoffman offers Design Your Standard or modifications fast so no special drilling or tapping procedures are required. The ability to use general purpose enclosures allows for modifications such as painting white or attaching a sunshield to reduce heat.
  • This alternative requires less “system” engineering than intrinsically-safe equipment.


  • Larger footprints allow for both passive and active cooling to reduce heat and humidity.
  • Hazardous location-rated Hoffman vortex coolers and Hoffman air conditioners may be used.
  • Corrosion resistant enclosures are also readily available.


  • Access and indication status is improved using purge and pressurization allowing easy access to electrical equipment for maintenance.
  • Continuous status indication is possible with local indicators and outputs.


  • This is a lower-cost solution for larger enclosures, compared to explosion-proof or flameproof enclosures.
  • These enclosures weigh less.

To read more about how purge and pressurization works, it advantages and limitations, download Hoffman’s white paper.



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