(71b) Using Ventilation to Reduce the Area Electrical Classification of Pilot Plants and Laboratories

All codes allow the use of ventilation to mitigate against the risk of a fire or explosion from flammable gases and vapors. The use of ventilation to reduce the area electrical classification of pilot plants nd laboratories is a well established practice. However, the risk mitigation is often poorly analyzed and often rests on questionable assumptions. This leads to the potential for inadvertently being at a higher hazard level than the organization realizes.

This presentation will address several issues regarding the effective use of ventilation to reduce the risk and hence allow a lower area electrical classification. Areas to be covered include:

• A brief summary of the code requirements
• A discussion of how ventilation can – and cannot – mitigate fire and explosion hazards
• A discussion of how hoods and ventilated enclosures often fail to contain the results of leakage, spills, and equipment failures including:
  • Inadequate design
  • Too low an exhaust rate
  • Over crowding
  • Poor exhaust distribution
• Some guidance on how to use ventilation effectively
• Guidelines on how to make ventilation effective