IDLH concentrations have been established by NIOSH for 387 chemicals (see above web site), please read the documentation presented for each chemical. Do not believe that the IDLH concentration means death. When using LC₅₀ data, NIOSH prefers a 30-min exposure and adjusts other data to an equivalent 30-min value using the following equation:

Adjusted LC₅₀ (30-min) = LC₅₀ (t) x (t/0.5) ^1/n

Where: LC₅₀ (t) = LC₅₀ determined over t hours

n = constant

The value for n selected by NIOSH is 3, based on a study by ten Berge (ten Berge, WF, Zwart, A and Appleman, L.M. Concentration-time mortality response relationship of irritant and systematically acting vapours and gases. J. Haz. Mat. 13, 301-309, 1986).