NPR 7910-1 Mechanical ventilation calculation for secondary sources of release

This calculator is free to use. Log in with an organisation to save calculations.

Calculation

Name

Description

Leak flow rate

Enter the volumetric leak flow in m³/h or m³/s, or convert from a mass flow in g/s or kg/s using molar mass and the NPR 7910-1 molar volume of 25 m³/kmol. The calculation always uses m³/h and g/s.

Volumetric flow Mass flow

Volumetric leak flow rate (a)

Converted volumetric leak flow rate (a)

m³/h ( m³/s)

a = value × 3600

Mass leak flow rate (a_m)

Molar mass (M)

g/mol

Converted volumetric leak flow rate (a)

m³/h ( m³/s)

a = a_m × (1/M) × 25 × 3.6

LEL and safety factor

Lower explosive limit (LEL)

vol%

Percentage of LEL (k)

Room size

Installed ventilation must be at least the higher of the NPR 7910-1 VC and 4 air changes per hour.

Room volume

m³

Minimum Required installed ventilation

m³/h

Governing value:

NPR 7910-1 VC: m³/h
VC at 4 air changes/h: m³/h
Volumetric leak flow rate (a): m³/h
Room volume: m³
LEL: vol%
k

VC = a × (100 / LEL) × (100 / k). Air-change VC = room volume × 4. Installed ventilation ≥ max(VC, air-change VC).