By Zachary Hachmeister, Chief Operating Officer, Fauske & Associates, LLC
20 Liter Chamber
The 8 ft3 exemption does not mean that an explosion hazard does not exist. In fact, the majority of data used for addressing dust explosion hazards is generated in a test apparatus with a volume of 20 L (~0.7 ft3). The exemption exists because it can be difficult to provide these small vessels with explosion protection equipment and that the hazard risk is considered to be modest. As an illustration, let us assume an 8 to 1 volumetric expansion from a typical dust deflagration, an 8 ft3 enclosure (sphere with a radius of 1 ¼ feet) can produce a fireball with a volume of 64 ft3. If the fireball is spherical then the radius would be ~2.5 ft. Therefore, the decision to strike a balance between the economic impact and potential consequence justified the exemption.
Hopefully, this provides some clarification to a frequently asked question. If you'd like to learn more about dust hazard analysis and mitigation, check out FAI's 3 Step Approach by clicking below.