MiniPID 2 HS Sensor Deployment Guidelines

Introduction
Photoionisation detection (PID) sensors enable measurements of a wide range of organic volatiles in air at concentrations ranging from parts per billion to low percentages. The full range of the HS MiniPID sensor is only 3000 ppb (3 ppm) isobutylene.  Isobutylene is universally used as a PID calibration gas.  In this document unspecified PID responses in ppb refer to an ppb isobutylene equivalent response calculated by frequent calibration of sensors with 2 ppm isobutylene. 

PID responses greater than ~3000 ppb cause a saturated HS MiniPID signal.  VOC readings >3000 ppb can be expected in some commonly encountered  environments, for example:

• Near heavy traffic, exacerbated by weather conditions or roadway architecture (eg urban canyons),  and at sites of unsealed refuelling  and fuel spillage (eg station forecourts).

• In industrial facilities where volatiles are routinely used in coatings and paint  preparations, or as a solvent.

• In clean rooms and heavily conditioned  or refrigerated environments where volatiles accumulate  due to low air turnover.

• In unventillated rooms and enclosed spaces where VOC’s have been allowed to accumulate.

• In domestic environments on occasion of heavy release of volatiles, such as from paints and varnishes, use of certain cleaning fluids or during cooking. 

By contrast, clean rural air delivers a PID response of less than 100 ppb.  In reasonably ventillated interior spaces at 20 to 25 oC (68 to 77 o F), 200 to 400 ppb is typical. However, these ambient levels increase significantly in the absence of ventillation and at higher temperatures

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