Argon is a colorless and odorless rare gas which is heavier than air. The most important chemical property of argon is its inertness, which makes it an ideal protective gas even at the temperatures commonly occurring in metallurgy and during arc welding. At high pressures, argon exhibits a "real" behaviour deviating from the ideal gas law. At 200 bar, for example, a gas cylinder contains approximately 7% more argon than expected in the case of an ideal gas. Argon is non-toxic but, just like nitrogen, is able to displace oxygen required for breathing. Moreover, because argon is heavier than air, it can accumulate close to ground level, particularly in depressions.