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5 Tips About Explosion Proof Refrigerators

If you work in a biotechnology lab, you most likely are aware that your potential for contact with explosive or flammable materials escalates. If you are wondering whether and when your lab should consider an explosion-proof refrigerator, now is the time for some answers before something untoward happens. The following paragraphs provide five quick tips.

Tip #1: Dangerous substances stored in refrigerators cause explosive reactions

Explosion-proof refrigerators are not commonly required in all laboratories. The availability of dangerous substances makes an explosion-proof refrigerator a necessary piece of equipment only in certain labs. Explosions of hazardous materials can cause damage to buildings, destroy research, and cause serious injury to laboratory staff.

In general, explosive reactions in substances are initiated by the application of four things:

  • Light
  • Heat
  • Mechanical shock
  • Catalysts.

For example, chlorine and hydrogen explode when exposed to light. Another example is that, among other things, mechanical shocks can set off explosions in the following chemicals:

  • Azides
  • Organic nitrates
  • Nitro compounds
  • Perchlorate
  • Peroxides.

Then, too, some metal ions act as an accelerant or catalyst for explosions as in the decay of peroxides.

Still other chemicals may self-react which means they can act in a forceful way to:

  • Form polymers,
  • Decompose, 
  • Forcefully condense from gas/vapor into a liquid form, or
  • Become unstable and automatically release light or heat without the help of oxygen.

Tip #2: Flammable materials are not safely stored in a household refrigerator

Despite what some people might think, it doesn’t take a lot of vapor or gas to cause an explosion. Explosions of flammable vapors are capable of destroying labs, blowing out windows, and sending lab remains flying. Sometimes explosions even ignite secondary fires and cause more damage. 

In 1982, a lab explosion resulted from petroleum ether improperly stored in a lab refrigerator. The ether was stored in tubes that were not sealed properly and the ether evaporated in a large enough amount that it exceeded the concentration necessary to breach the flashpoint. An internal switch or thermostat in the refrigerator most likely caused the ether to explode. The lab room sustained $11,000 in damages and $25,000 in equipment destroyed. At today’s prices, the damages would exceed $250,000.

Tip #3: Several bad reasons for using household or typical lab refrigerators

A typical lab refrigerator has several “electrical ignition points“, making it a bad choice for storing explosive or flammable materials. Household refrigerators may create arcs, sparks, or full-out flames inside the refrigerator during normal operation. Those arcs, sparks, or flames may leak to the outside and cause flammable vapors/gases in the room to ignite.

Fabricators specially modify the design of an explosion-proof refrigerator so that it is less likely to spark an explosion. Shields surround light sources.  Compressor and motor wires safely stow away inside insulated walls or store in an enclosure completely outside the unit.

Especially important, hazardous materials (sometimes known as a hazardous location) refrigerators do not have a power cord. Instead of plugging directly into a wall socket, the explosion-proof refrigerator is hard-wired using rigid circuits directly into the facility’s 120 VAC electrical system. That feature eliminates the chance that sparks from an electrical short or overheating will cause a flammable or explosive material inside the refrigerator to burst into flames. It also means that installation requires a qualified electrician to connect the explosion-proof refrigerator to an exclusive power source.

The basic difference between a traditional refrigerator and an explosion-proof refrigerator is that the latter has a spark-free interior and a spark-free exterior in order to prevent any flammable gases or vapors that gather outside the refrigerator from exploding.

Tip #4: Comparing the cost of an explosion-proof refrigerator to household refrigerators

Explosion-proof refrigerators are often prohibitively expensive when compared to traditional lab refrigerators or household refrigerators. Explosive-proof units are considered an essential necessary expense because they prevent situations that may cause damage to facilities and personnel. Their expense is why they are only for those labs whose processes produce flammable gases or unstable materials.

In other words, an explosive-proof refrigerator is required only when the outside conditions are as precarious and unpredictable as the inside conditions. This often refers to flammable liquids, gases, or solids with less than a 100-degree Fahrenheit flashpoint. For example, solvent dispensing rooms and paint booths must use these special UL approved refrigerators because a flammable condition may occur at any time.

Tip #5: OSHA regulations on explosion-proof refrigerators

Explosion-proof refrigerators must meet National Fire Protection Association (NFPA) and Occupational Safety and Health (OSHA) standards that speak to safe storage of volatile materials, such as solvents. OSHA requires that employers and staff follow the requirements of its electrical standards for hazardous areas which appear in regulation 1910.307.  OSHA classifies hazardous areas depending on the chances that the area contains flammable vapors, gases, or liquids in high enough concentrations that the area’s conditions may give rise to a flammable or combustible event.

Laboratories, like other industrial employers, are subject to OSHA’s Occupational Safety and Health Standards regarding explosion-proof electrical equipment. OSHA defines explosion-proof equipment as equipment that is bound by a case built to withstand an explosion of gas or vapor inside the equipment.

OSHA also requires that the case is capable of preventing the gases or vapors outside the equipment from bursting into flame from sparks, flashes or explosion of the inside contents. Such equipment must operate at a temperature that will not start a fire in the surrounding flammable space.

OSHA defines areas that require explosion-proof equipment as Class I locations. They are also known as hazardous locations. Class I locations are those areas in which ignitable concentrations of flammable liquids, vapors, or gases in the air exist under normal operating conditions. Labs that deal with explosive liquids, gases, and vapors that accumulate in the space qualify as hazardous locations.

OSHA requires that employers prove that explosion-proof equipment provides the needed protection from hazardous combustibility of flammable vapors, liquids, and gases.

Moving Forward

If you are considering buying an explosion-proof refrigerator, we invite you to view our standard hazardous location models. Naturally, the products meet National Fire Protection Association (NFPA) and Occupational Safety and Health (OSHA) standards for flammable material units in hazardous locations Class I, Division II, Group C and D.

To learn more about handling chemicals in explosion-proof refrigerators, you may enjoy the article from entitled “Handling and Storing Chemicals.”


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