readily. Safety Oxyacetylene welding/cutting is not difficult, but there are a good number of subtle safety points that should be learned such as: More than 1/7 the capacity of the cylinder should not be used per hour. This causes the acetone inside the acetylene cylinder to come out of the cylinder and contaminate the hose and possibly the torch. Acetylene is dangerous above 1 atm (15 psi) pressure. It is unstable and explosively decomposes. Proper ventilation when welding will help to avoid large chemical exposure. The importance of eye protection Proper protection such as welding goggles should be worn at all times, including to protect the eyes against glare and flying sparks. Special safety eyewear must be used—both to protect the welder and to provide a clear view through the yellow-orange flare given off by the incandescing flux. In the 1940s cobalt melters’ glasses were borrowed from steel foundries and were still available until the 1980s. However, the lack of protection from impact, ultra-violet, infrared and blue light caused severe eyestrain and eye damage. Didymium eyewear, developed for glassblowers in the 1960s, was also borrowed—until many complained of eye problems from excessive infrared, blue light, and insufficient shading. Today very good eye protection can be found designed especially for gas-welding aluminum that cuts the sodium orange flare completely and provides the necessary protection from ultraviolet, infrared, blue light and impact, according to ANSI Z87-1989 safety standards for a Special Purpose Lens. Safety with cylinders Fuel and oxygen tanks should be fastened securely and upright to a wall, post, or portable cart. An oxygen tank is especially dangerous because the gas is stored at a pressure of 21 MPa (3000 lbf/in² = 200 atmospheres) when full. If the tank falls over and damages the valve, the tank can be jettisoned by the compressed oxygen escaping the cylinder at high speed. Tanks in this state are capable of breaking through a brick wall. For this reason, never move an oxygen tank around without its valve cap screwed in place. On an oxyacetylene torch system there are three types of valves: the tank valve, the regulator valve, and the torch valve. Each gas in the system will have each of these three valves. The regulator converts the high pressure gas inside of the tanks to a low pressure stream suitable for welding. Acetylene cylinders must be maintained in an upright position to prevent