NTP (Normal Temperature & Pressure) Definitions


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

(TLV)

29.92 “Hg

760 mm Hg

530 ˚R

298 ˚K

NIOSH/AIHA

(Traditional)

29.92 “Hg

760 mm Hg

537 ˚R

298 ˚K

ASHRAE

(Ventilation)

29.92 “Hg

760 mm Hg

528 ˚R

293 ˚K

Source: Useful Equations, Practical Applications of OH&S Match: D. Jeff Burton, PE, CIH