---
title: Principles of Operation
description: "The basic principle of operation involves raising and maintaining the internal pressure of the enclosure to a level slightly above the atmospheric pressure outside the enclosure. This ensures that any flammable gases or vapours cannot enter. The minimum over-pressure specified…"
url: "https://www.eicstech.com/kb/pressurisation-ex-p/basics-on-principles-of-operation-for-pressurisation/"
updated: "2022-06-01"
category: Explosion Proof Basics / Pressurisation (Ex p)
---

# Principles of Operation

The basic principle of operation involves raising and maintaining the internal pressure of the enclosure to a level slightly above the atmospheric pressure outside the enclosure. This ensures that any flammable gases or vapours cannot enter. The minimum over-pressure specified in standards is 50 Pa (**0.5mBar**) for types **px** and **py**, and **0.25mBar** for type **pz**.

The safe gas used to provide the over-pressure will normally be air, but an inert gas such as nitrogen may also be used where necessary

Note:     The manufacturer shall specify the minimum and maximum normal overpressure in service, the maximum overpressure during purging and the maximum leakage rate at the maximum normal overpressure.

![principle of operation](https://www.eicstech.com/wp-content/uploads/2022/06/principle-of-operation.png)