total organic carbon (TOC) & VOC meter idea to help detect mixed gas volatile organic compound (VOC) levels as part of an indoor air quality (IAQ) maintenance program. Volatile Organic Compounds (VOCS) are carbon based compounds that pose a significant health hazard due to their toxicity. VOCs in large concentrations can easily be present in the air without us always knowing due to lack of odor or color. Other VOCs in higher concentrations are readily noticeable by odor such as gasoline vapors which are comprised of several different VOCs. Even very small levels of VOCs over a period of time can cause long term damaging effects to human health and thus must be monitored. Some VOCs, if allowed to reach high concentrations, can be extremely volatile and sometimes combustible. The proper monitor can be selected depending upon what anticipated VOCs there are to be present. A Photo Ionization Detector (PID) can analyze a wide range of chemicals, including aromatic hydrocarbons, but excluding low molecular weight hydrocarbons. PID works by using ultraviolet light to break down airborne VOCs into either positive or negative ions. Once broken down, the detector can then measure or detect the charge of the ionized gas. It should be mentioned that PID only temporarily changes the VOC sample it detects and does not permanently change them. Methylene chloride is an example of a dangerous VOC PID is useful in detecting.