Explosion vent, explosion hatch – roof hatch or wall hatch?

A risk assessment and safety report is obligatory to protect the employees in all buildings where the risk of an explosion is present or possible. This can make an explosion vent or hatch necessary. European regulations (ATEX guidelines) provide instructions for protecting employees in locations where an explosive atmosphere may be present. The degree of risk is defined and categorised. The equipment and safeguards used must match the defined hazard category.


What is an explosion vent or hatch?

An explosion vent or hatch, also called a relief flap, seals an opening in the roof or facade. The explosion vent or hatch must open immediately if there is a pressure increase. Directive 1994/9/EC, article 3.1.5 describes a suitable pressure-release device. “Suitable” means that the opening(s) must be large enough to release the pressure wave from an explosion quickly in order to protect the structure of the building and the people inside. The size of the opening(s) and the number of explosion vents/hatches needed have to be calculated by an expert. It is necessary to take into account the nature of the explosion (gas or dust), the location of the openings in the building, the theoretical behaviour of the pressure wave, the construction of the building and the layout of the area where the explosion could occur.


To protect humans and animals, you also need to allow for the potential escape of dangerous or poisonous substances, as well as objects or parts flying through the relief flap. If there is no solution, the zone around a building may be declared a hazard area.


Requirements of relief flaps

An explosion relief flap or flaps must comply with the provisions of BS-EN 1991-1-7:2006. Relief flaps from Gorter in the form of aluminium roof hatches or facade elements are fitted with a patented Explosion Release Control (ERC) that ensures the explosion vent opens quickly and at the right time when a preset excess pressure is reached. Depending on the situation, the hatches are normally used for roof or facade access.


  • The mechanical strength of the Gorter explosion vent is tested at an under- and over-pressure of 3,000 Pa (SKG report 04.1001).
  • The Explosion Release Control unlocks the hatch if the pressure increases by about 100 kg. This setting is based on the recommendations of the NFPA 68 Guide for Venting of Deflagrations 2002. Publisher: National Fire Protection Association (USA). The Explosion Release Control is tested by the Amolf Instituut (part of the FOM Institute) in Amsterdam.
  • The weight of the relief flap is below the requirements of BS-EN 1991.
  • Gorter hatches are supplied with KOMO® certification.


Maintenance and warranty of explosion-release hatches

Depending on the kind of soiling, the maintenance of an explosion-release roof or wall hatch is limited to regular cleaning and lubrication of the moving parts with Teflon. Its efficient operation can be checked during cleaning and any faulty parts replaced immediately. Gorter roof hatches come with a 10-year warranty.



Explosion-release roof and wall hatches

More information on explosion-release roof, wall hatches and vents can be found in the menu under explosion-release roof and wall hatches. You can also contact Gorter for additional information or a quotation.