 Generally , in cabinets or display cases that are entirely or partially made of wood , the hydrolysis of acetyl groups in the wood <unk> creates acetic acid . The rate at which the acetic acid is produced is proportional to the concentration of esters in the wood , the humidity , the temperature , and the overall acidity of the environment . Acidic fumes can also be released from formaldehyde which can occur in wood as a degradation product of lignin . Acidic fumes can also be given off from ubiquitous formaldehyde resins ( commonly urea @-@ formaldehyde resins ) . 
