What are some common measurements of odor/odor intensity?


There are four common methods of expressing the intensity/concentration of odor within a system. These are the Perceptibility Threshold (ATC: Absolute Threshold Concentration), Odor Number (TON: Threshold Odor Number), Maximum Exposure Concentration (TVL: Threshold Limit Value), and Maximum Allowable Concentration (MAC). A description about each can be found below:Perceptibility Threshold (ATC): ATC is the minimum concentration that is detectable by 100% (some cases only up to 50%) of persons participating in a sense of smell analysis. Imagine 100 people are in a room. The ATC concentration would be the concentration of smell that is detected by all 100 people in the room. This means there is no question as to whether there is an odor.Odor Number (TON): TON is the number of dilutions needed to reduce the current concentration of smell to ATC. This means that the current concentration of odor is more than the ATC and must be diluted to get to the threshold. The amount of dilutions (which is a preset value used in a laboratory) needed to reduce this concentration is the TON.Maximum Exposure Concentration (TLV): TLV is the maximum concentration a person can be exposed to for 8 hours a day, 5 days a week and 50 weeks a year for a work life of 40 years. Maximum Allowable Concentration (MAC): Is a preset concentration that should never be exceeded. This is defined by the agency governing the concentration. Below is a chart showing some common amounts of concentration for the categories above: