Air & Ventilation Guide
Estimate the airflow moving through a passage, and a rough CO₂ build-up if your group sits in a poorly ventilated chamber for a while — a planning aid, not a real-time air-quality reading.
Airflow & air-quality estimate
✅ Adequate — CO₂ build-up stays low for this group and sit time.
Two linked estimates
The first half of this tool is straightforward volumetric flow: cross-section times air speed gives a volume of air moving per minute, converted to an hourly rate and to air changes per hour for a reference chamber. Faster air, or a bigger passage, means more air turning over.
The second half models what happens if that airflow stops — a still pocket where a group's own breathing is the only thing changing the air's composition. Combining a standard CO₂ production rate with group size and sit time gives a rough estimated concentration, flagged as adequate, caution, or poor against widely used indoor air-quality reference points.
Frequently Asked Questions
How is airflow through a passage calculated?
Airflow is the passage's cross-sectional area (its width times its height) multiplied by the air's speed through that section. The result is a volume of air per minute, which this tool also converts to an hourly rate and, given a reference chamber volume, to air changes per hour — a common way to describe how thoroughly a space's air turns over.
Where does the CO2 build-up estimate come from?
It uses a standard per-person CO2 production rate — higher for harder exertion — multiplied by the group size and how long they sit in the space, then spread across the chamber's volume as if the air were completely still. Adding that to typical background CO2 gives a rough estimated concentration.
Why does the tool assume a 'still' chamber for the CO2 estimate?
It's a worst-case planning assumption: if there's genuinely no effective air movement through a chamber, CO2 from breathing has nowhere to go and simply accumulates. In reality, most cave passages have some air movement, which disperses CO2 far more effectively than this static estimate assumes — treat a 'poor' result as a prompt to check real conditions, not a precise reading.
Should I carry a real gas meter instead of trusting this estimate?
Yes, for any trip into a known or suspected poor-air area — a personal CO2 or O2 meter gives you an actual reading on the day, which this planning tool cannot. Use this calculator to think through a trip in advance, and a real meter to make the actual go/no-go call underground.
Planning estimate only, not a safety certification. Carry a real gas meter for any trip into a known or suspected poor-air area, and turn back if conditions feel wrong regardless of what any calculator says.