A few questions have arisen regarding the term NTP (Normal Temperature and Pressure).  The following table helps to sort any potential confusion.

Agency Pressure Temperature Traditional

(Chemistry/Physics) 29.92 “Hg

760 mm Hg 492 ˚R

273 ˚K ACGIH

(Ventilation)

29.92 “Hg

760 mm Hg 530 ˚R

294 ˚K NIOSH/AIHA

(Traditional) 29.92 [...]