Variables
Description
What is this formula?
This formula evaluates how effectively a ventilation system removes contaminants from an occupied space by comparing contaminant concentrations in the supply air, breathing zone, and exhaust air.
When to use it
Use it when assessing indoor air quality performance, HVAC system effectiveness, contaminant removal efficiency, and ventilation design quality.
Example
Data:
Ce = 120 µg/m³
Cs = 10 µg/m³
Cb = 90 µg/m³
Formula:
Ev = (Ce − Cs)/(Cb − Cs)
Substitution:
Ev = (120 − 10)/(90 − 10)
Ev = 110/80
Result:
Ev = 1.375
Applications
HVAC design, indoor air quality assessment, clean rooms, hospitals, laboratories, office buildings, schools, and sustainable building certification.
Note
This formula is a performance indicator used in ventilation engineering. Values greater than 1 generally indicate that contaminants are removed more efficiently than predicted by a perfectly mixed air model, while values below 1 may indicate poor contaminant removal or short-circuit airflow patterns.