Q: What is a PID?

A: A photo-ionization detector or PID, uses an electrodeless ultraviolet lamp to ionize chemicals with ionization potentials (I.P) below the range of the lamp and thereby measure their concentrations in parts-per-million (ppm). A PID is best used to detect low levels (0-2000ppm) of broad band toxics or volatile organic compounds (VOCs).

Sample Site Remediation Procedure using PID: Prior to use, the PID was calibrated against a 100 parts per million (ppm) isobutylene span gas in air matrix. The instrument was then zeroed against the ambient air near the work area. The PID is useful for qualitative field screening of VOCs and provides a basis for comparison between soil samples collected in the field. Soil samples were placed into sealable plastic bags and allowed to sit in a warm area for volatilization to occur. Each bag was opened and the tip of the PID was inserted into the head space above each sample.

Click HERE to view a document on a PID.

Click HERE to view a document on Measuring VOCs.

Q: What are some examples of chemicals that are detected by PIDs?

A: Acetone, Ammonia, Asphalt fumes, Benzene, Butane, Chlorobenzene, Cyclohexane, Diesel Fuel, Ethyl ether, Ethylene glycol, Formaldehyde, Gasoline, Hexane, Iodine, Isobutylene, Jet fuels, kerosene, Methyl Mercaptan, Mineral Spirits, Nitric Oxide, Octane, Pentane, Propylene, Resorcinol, Styrene, Toluene, Turpentine, Vinyl Chloride, etc.

For a more exhaustive, partial list of VOCs detected by a PID with a 10.6 eV lamp, click HERE.

Q: What are VOCs?

A: VOCs are Volatile Organic Compounds, organic chemicals that have a high vapor pressure and easily form vapors at normal temperatures and pressure.

The term "organic" indicates that the compounds contain carbon. VOC exposures are often associated with an odour while other times there are no odours. Both can be harmful.

The term is generally applied to organic solvents, certain paint additives, aerosol spray can propellants, fuels (such as gasoline, and kerosene), petroleum distillates, dry cleaning products and many other industrial and consumer products ranging from office supplies to building materials. VOCs are also naturally emitted by a number of plants and trees.

Q: What are the effects of VOC exposure?

A:

Key signs or symptoms associated with exposure to VOCs include conjunctival irritation, nose and throat discomfort, headache, allergic skin reaction, dyspnea, declines in serum cholinesterase levels, nausea, emesis, epistaxis, fatigue, dizziness.

The ability of organic chemicals to cause health effects varies greatly from those that are highly toxic, to those with no known health effect. As with other pollutants, the extent and nature of the health effect will depend on many factors including level of exposure and length of time exposed. Eye and respiratory tract irritation, headaches, dizziness, visual disorders, and memory impairment are among the immediate symptoms that some people have experienced soon after exposure to some organics.

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