This document provides examples of converting between parts per million (ppm) and milligrams per cubic meter (mg/m3) for occupational health hazard calculations. It defines molecular weight and notes the molar volume of air used is for normal temperature and pressure conditions. Worked examples are given to demonstrate converting between the concentration units of ppm and mg/m3.

1. UNIT 3 CONCENTRATION CONVERSION CALCULATION EXAMPLES HPEO 408 Occupational Health Hazards

2. ppm ↔ mg/m 3 CONVERSIONS Where: MW = molecular weight of substance in g/mol 24.45 = molar volume of air in liters at normal temperature and pressure ( NTP ) NTP = Temperature (25 o C) Pressure (1 atm / 760 mm Hg) NOTE: if not NTP conditions molar volume may require adjustment

3. EXAMPLE 1

4. EXAMPLE 2