CO₂ to Enrich a Sealed Room

Ambient air is about 420 ppm carbon dioxide, and most crops photosynthesise faster with more. Enrichment to 800–1,500 ppm typically raises growth rates 20–30% provided light, water and nutrients are not the limiting factor first — which is the whole catch, because in a dim room CO₂ buys nothing at all.

The mass needed is straightforward: room volume times the concentration increase times the density of CO₂, about 1.81 kg/m³ at 25 °C and one atmosphere. A 10 m³ tent lifted from 400 to 1,000 ppm needs only 10.8 grams. That figure surprises people, and it is why the practical problem is never the initial charge but the leak rate — a typical room loses its enrichment within tens of minutes, so the ongoing supply dwarfs the first dose.

Enrichment only makes sense in a sealed space, since ventilation discards it immediately, and a sealed space must then reject its heat mechanically. The practical trigger is Liebig's law of the minimum: raise CO₂ only when light is already at or above the crop's saturation point, otherwise the limiting factor is still photons and the gas is wasted.

The safety point is not a footnote. Carbon dioxide is an asphyxiant, and the concentrations at which it harms people are lower than most growers assume: 5,000 ppm is the standard occupational limit for an eight-hour day, symptoms appear around 30,000 ppm, and higher levels can be fatal quickly. It is heavier than air and pools at floor level in still rooms. Any enriched space needs a monitor with an alarm, a controller with a hard ceiling, and the discipline to ventilate before entering.