Key Questions
The following key questions are answered in this module:
What is the purpose of air monitoring?
Air monitoring is required to select appropriate PPE, establish hazard control zones, assess potential health effects of exposure, and determine the need for medical monitoring and decontamination. Upon initial site entry, air monitoring is needed to determine if the atmosphere is flammable, oxygen-deficient, or immediately dangerous to life and health (IDLH).
What are direct-reading instruments?
Direct-reading instruments measure the concentration of contaminants as air is sampled in the field versus collecting samples and measuring them later in a lab.
What is the difference between %, ppm, mg/m3?
Percent (%) is the proportion of gas molecules out of 100 molecules of gas and air. PPM is parts per million and is essentially the same as percent but out of one million molecules instead of 100. Typically, ppm is used for concentrations under 1% (10,000 ppm). Mass per unit volume, typically expressed in units of mg/m3 is used for concentrations of particulates in air.
What is a multi-gas detector?
Multi-gas detectors can have several different types of sensors. Most multi-gas detectors can detect combustible gases, oxygen, and at least one toxic gas.
What is the difference between a bump test and a calibration check?
A bump test involves exposing a sensor to a test gas of a sufficient concentration to cause the device to alarm. It is a qualitative function test. A bump test does not determine an instrument's accuracy. A calibration check involves exposing the sensor to a test gas of a known concentration. A reading within 10% of the calibration gas concentration is usually acceptable.