Unit-consistent ACH conversion
Airflow from Specified Air Changes per Hour
Convert a documented room volume and an ACH requirement selected from the applicable code,standard or design basis into airflow units. This calculator does not recommend ACH or select a fan.
Required volumetric flow for the supplied ACH
The CDC defines ACH as airflow rate divided by room volume,expressed per hour. WHO gives the equivalent relationship between L/s,room volume and ACH. Therefore,for volume В in m³ and ACH Н in h⁻¹:
The former title claimed Q=V×ACH/60 while reporting m³/h. Division by60 instead gives m³/min,not m³/h;that hidden claim has been removed.
CFM uses the international-foot conversion derived from NIST SP811:1ft=0.3048m exactly,so 1CFM=1.69901079552m³/h.
No universal ACH table: requirements depend on jurisdiction,space use,occupancy,hazard/process,pressure relation,outdoor versus total/clean airflow and the applicable edition. The removed office/kitchen/warehouse/lab/hospital ranges and “supply=exhaust±10%” rule cannot be applied universally.
The ideal interval 60/N is only the time corresponding to one nominal room volume. It is not contaminant-removal time;actual removal depends on mixing,source behavior and clean-air effectiveness.
Airflow alone does not select a fan. Selection also requires the system pressure/curve,air density,operating point,efficiency,motor margin,sound,temperature/material limits and control arrangement.
Извори:CDC ACH definition;WHO ventilation-rate relationship;NIST SP811 conversions.
