Monitoring carbon dioxide in addition to temperature and humidity is critical to maximizing mushroom growth.
Carbon dioxide (CO2) is produced during the mushroom's growth in compost, which negatively affects mushroom growth during pinning. This makes proper ventilation required. Pinning is the trickiest part for a mushroom grower, since a combination of CO2 concentration, temperature, light, and humidity triggers mushrooms towards fruiting.
Carbon dioxide concentration becomes elevated during the vegetative growth phase, when mycelium is sealed in gas-resistant plastic barriers or bags to trap gases produced by the growing mycelium. To induce pinning, the barrier is removed. CO2 concentration then decreases from about 0.08% to 0.04% (800ppm to 400ppm - the ambient atmospheric level). Therefore a 0-2,000ppm CO2 level meter is best for mushroom growing applications.