Mushroom fruiting bodies or pins are small outgrowths from the rhizomorphs, which form, in the casing layer. These fruiting bodies continue to grow larger through a button stage, and ultimately enlarge into a mushroom. Harvestable mushrooms appear 16 to 21 days after casing. Pinning affects both the potential yield and quality of a crop. The management of water content of the casing, relative humidity, and carbon dioxide content of the air are all essential in determining crop yield and quality. We must measure these and other factors like temperature and air flow 4 to 5 times in each room over a 24 hour period.