CO₂ Breathing Emission Calculator

The core mathematical model balances the rate of carbon dioxide generated by occupants against the rate at which fresh air flushes out the room. First, the room volume ($V$) is derived from its floor area and ceiling height. The resulting CO₂ concentration ($C$) at any given duration is computed using an exponential decay and accumulation function: $C = \frac{Q \cdot G}{V \cdot A} \cdot (1 - e^{-A \cdot t}) + (C_{added} - C_{initial}) \cdot e^{-A \cdot t} + C_{initial}$, where $G$ represents the generation rate per person, $Q$ is the number of occupants, $A$ is the air changes per hour, and $t$ is the duration. Concentrations are then translated into parts per million (PPM) or percentage values for easy interpretation against safety guidelines.

Imagine a meeting room that is 5 meters long, 4 meters wide, and 3 meters high, resulting in a room volume ($V$) of 60 cubic meters. Four people are working inside with a moderate activity generation rate, and the HVAC system provides 2 air changes per hour ($A = 2$). Over a duration ($t$) of 1 hour, starting from a baseline outdoor ambient concentration of 400 PPM ($0.0004$), the tool applies the exponential formula. The resulting indoor concentration rises to approximately 850 PPM after 60 minutes, a safe level well below standard indoor thresholds of 1,000 PPM.

To keep indoor carbon dioxide at healthy levels, ensure that your ventilation system matches maximum occupancy expectations. Routinely check and replace HVAC filters to maintain target air change rates. If rooms lack mechanical ventilation, schedule periodic manual airing by opening windows during high-occupancy events to prevent cognitive fatigue caused by rising CO₂.