Hazards of Acetylene

Acetylene is the most commonly used gas for fueling cutting and welding torches.  The very molecular structure of acetylene is what makes the gas both ideally useful and hazardous. Each molecule consists of two carbon atoms and two hydrogen atoms that are held together by a triple carbon bond. This unstable bond stores a lot of energy. When acetylene is mixed with oxygen and the bond is broken, the result is the high temperatures needed to melt metal alloys. The temperature of the flame from the mixture can reach over 5700°F!

Generally, the men and women who use acetylene torches are familiar with the fire hazards associated hot flames and the production of hot slag. However, there are many unique characteristics of acetylene itself that create special hazards compared to other fuel gases. This gas has the widest explosive range of any commonly used gas. When mixed with air, the explosive range is from 2.5% to 82%. Acetylene leaks, no matter how small, can have serious consequences.

Some tips for safely using and storing acetylene:

  • Always use acetylene in a well vented area, and never in a confined space.
  • When using around electrical equipment, research the National Electric Code’s special designation for using electrical equipment around acetylene.
  • Acetylene should never be allowed to come into contact with certain metals such as unalloyed copper.
  • Do not store or use acetylene at pressures greater than 15 psi. Cylinder pressures are rated for 250 psi but this is acceptable because the gas is dissolved in acetone.)
  • Bleed the gas from the regulator by closing the cylinder valve before shutting off the regulator, to permit gas to bleed from the regulator.
  • Always cap and secure stored cylinders upright to prevent them from falling over and damaging the valve or cylinder.
  • Acetylene cylinders are not hollow. They are packed with porous rock that is saturated with acetone. Acetylene is dissolved in the acetone. As a result, cylinders should only be used or stored in an upright position. This prevents possibility of the acetone leaking from the cylinder. If this is not possible, rest the cylinder upright for one-half hour before using. This prevents liquid acetone from running through your regulator during use.
  • Do not store cylinders near open flames or electrical equipment. Never store acetylene, or any other fuel gas, within 25 feet of oxygen cylinders. If this separation is not possible, erect a noncombustible (1/2-hour fire rated) partition, at least five feet high, between the two gases in storage.

Remember, improperly handling compressed gases can lead to serious fires, explosions, or releases due to pressure buildup in cylinders or reactions with other materials. Always use correct procedures for handling and using acetylene gas. Talking about the hazards and proper handling and storing procedures with your coworkers reduces the risk of an incident.