Process or storage vessels and pipe systems that contain ignitable ranges of oxygen and flammable vapors are susceptible to catastrophic explosions. If the oxygen and vapor mixture is ignited by sparks, arcs, friction, compression or other heat sources, the expanding flame front may cause significant injuries and damage. One method of lessening the likelihood of a flash fire is by the installation of a flame arrestor in the equipment or on the end of a vent or process line. Flame arrestors are used in many industries, including refining, oil exploration and production, pharmaceutical, chemical, petrochemical, pulp and paper, sewage treatment, landfills, mining, power generation, and bulk liquids transportation.
Yes, OSHA has rules for the use of flammable liquids in areas that are not designed as a Hazardous Location. OSHA covers Hazardous Locations in 1910.307, but those areas that do not rise to the level of being a Hazardous Location fall under 1910.334(d) which states:
This is an excellent photo that shows what happens when a FLAMMABLE LIQUIDS ATMOPSHERIC STORAGE tank does not have proper or adequate emergency venting. As we can see in this photo (Source: AP) the tank is still in tank, but with a large hole (e.g. new vent!). This tank was estimated to have reached the height of 60' and landed approximately 75 yards from its foundation. Ignition was a lighting strike.
OSHA, as well as NFPA and IFC, permit a "weak roof-to-shell seam" as the means for emergency venting on an OUTSIDE ABOVE GROUND ATMOSPHERIC storage tank for flammable liquids. This method was vey common in the early days, but has since been replaced with engineered fire vents. This video does an excellent job demonstrating how a "weak roof-to-shell seam" works and why emergency responders MUST be aware of how a flammable liquid tank will vent when involved in a fire scenario. The video at the bottom of the page shows what happens when the "weak roof-to-shell seam" does NOT work as designed. This same video then demonstrates a proper "weak roof-to-shell seam" working and we should take notice of the distance this tank roof travels!