Carbon dioxide production peaks in the first two flushes, when DMR measures about 10 g of carbon dioxide per square metre of bed per hour.
For that period DMR asks for about 6 air changes per hour, with the fresh air vent at 30 per cent and 70 per cent recirculated. From the third flush, 4 air changes per hour hold oxygen near 16 per cent and fresh air drops to 20 per cent. Room carbon dioxide during cropping sits at 1000 to 1500 ppm.