Pressurized enclosures and combustible dusts

As explained in Section 2.5 and Table 2.5, the relevant standards ask for a certain tightness of the enclosure against the ingress of dust and a surface temperature ensuring a certain margin of safety related to the glow temperature and ignition temperature of the combustible dust referred to. 

Attention should be directed to the airlock concerning the dragging of dust deposits on clothes or shoes to the airlock s interior. Cleaning procedures may be required, e.g. by an air shower, to avoid dust that may be transported into the pressurized rooms. 

Pressurization techniques are similar to those used in zones 1 and 2, with the exception that purging shall not be applied. The high flow rate of protective gas during the purging period accompanied by a high velocity of gas may stir up dust layers inside the p-room on components and thus adversely affect the safety of this type of protection. Static pressurization, leakage compensation 

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