Our sense of smell is activated when the nose captures odor-causing chemicals, called odorants, from the air.
Nerves located in the nose pass a message on to the brain when they detect an odorant.
The brain then analyzes the message about the odorant. Scientists have identified hundreds of odorants forming the collection of smells known as farmstead odors. Table 1 is a partial list of the groups of odorants released by animals and by breakdown of manure. Under each group is a list of individual chemical compounds that are commonly found in manure odors. The brain makes decisions about the odorant at certain concentrations.