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 V in m³ and ACH N 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.
Sources:CDC ACH definition;WHO ventilation-rate relationship;NIST SP811 conversions.
Nikolai Shelkovenko
Nikolai Shelkovenko is a vibration analysis engineer and the founder and CEO of Vibromera. For more than 15 years he has balanced rotating equipment in the field rather than on a test bench: mulchers, industrial fans, crushers, centrifuges, shafts and spindles. That work is what the Balanset instruments grew out of — they were designed as a tool a specialist can carry to the machine and use alone, on site, not as laboratory equipment. Vibromera was founded in 2017 and has been based in Porto, Portugal, since 2023. Development, assembly and support of the Balanset line all happen here. The flagship instrument is the Balanset-1A, a portable analyser for single- and two-plane balancing and for vibration diagnostics. Nikolai is personally involved in customer support, in working through difficult balancing cases and in the development of the software. He works with customers worldwide, in any language.
