CONFINED SPACE · PLANNING TOOL
VENTILATION
PLANNER.
Space volume. Rated airflow. Nominal air-change time.
A transparent calculation for your planning conversation.
01 DEFINE THE SPACE
Fictional example loadedUse the internal dimensions of the space.
02 SET RATED FLOW
Use the blower’s rated flow. No duct-loss correction is applied.
Add equipment & activity notes Optional
Notes stay in this session and do not change the calculation.
03 NOMINAL ESTIMATE
RATED FLOWInputs, formulas, results & limitations in one plain-text record.
View plain-text record
THE CALCULATION, IN PLAIN SIGHT
VOLUME ÷ RATED FLOW = TIME
One nominal air change is the space volume divided by the blower’s rated flow per minute. Multiply by your target changes for nominal runtime. Nominal ACH is rated flow × 60 ÷ volume.
This ratio does not establish contaminant removal or acceptable entry conditions.
What this estimate cannot tell you
Duct layout, restrictions, mixing, dead zones, blower performance, and ongoing contaminant sources affect actual ventilation. This tool does not model delivered flow or contaminant removal. A target count is a planning input, not an entry criterion.
Cylinders represent full cylindrical geometry. Use an explicit custom volume for partial fill or irregular occupied volumes.
OSHA references & review boundary
Construction: 29 CFR 1926.1203 (Subpart AA). General industry: 29 CFR 1910.146. These are distinct standards; select the applicable procedure for the work.
1910.146 Appendix B addresses atmospheric testing. A volume/flow calculation does not replace it. See also OSHA’s confined spaces overview.
References checked September 8, 2026. Qualified confined-space safety review, industrial-hygiene review where appropriate, and content/legal review are required before public release. No reviewer sign-off recorded.