Skip to main content

The Clean Air Sarnia and Area (CASA) monitoring network includes continuous (real-time) and non-continuous air quality monitoring equipment.

Real-Time Monitoring Equipment

Real-time monitoring equipment is employed throughout the CASA network for the following parameters:

NO2 - Nitrogen dioxide is measured using a nitrogen oxides analyzer , which uses the principle of chemiluminescence detection.

O3 - Ozone is measured using a UV adsorption analyzer.

SO2 - Sulphur dioxide is measured using a UV fluorescence analyzer.

TRS - Total reduced sulphur is measured using a UV fluorescence analyzer.

PM2.5 - Fine particulate matter is measured using a SHARP or BAM particulate monitor.

VOC - Volatile organic compounds, specifically 1,3-butadiene and benzene, are measured using a gas chromatograph/mass spectrometer (GC/MS).

Wind Speed/Wind Direction - Wind conditions are measured using an anemometer, which provides information on wind speed and wind direction.

Air Quality Monitoring Equipment

Non-Continuous Monitoring

Non-continuous monitoring involves collecting samples which are sent for laboratory analysis. Non-continuous monitoring equipment is employed throughout the CASA network for the following parameters:

TSP and metals - Total suspended particulate and metals sampling uses a high-volume air sampler that draws air through a sample filter that captures particulate matter containing metals. The sample draws air through the filter for a 24-hour period, and then the filter is analyzed at a laboratory.

VOC - Volatile organic compound samples are collected into a specially prepared evacuated canister (SUMMA canister). The samples collect air over a 24-hour period, and then the canister is sent to a lab for analysis using a Gas Chromatography/ Mass Spectrometer (GC/MS).

PAH - Polycyclic aromatic hydrocarbon samples are collected using a high volume sampler with a Teflon filter. The sampler draws air through the filter for a 24-hour period, and then the filter is sent to a laboratory for analysis using a Gas Chromatograph/ Mass Spectrometry (GC/MS).

SUMMA canister

Other Monitoring Equipment


An Airpointer is a compact air monitoring station that can measure and report on pollutant concentrations on an hourly basis. Airpointers typically measure common air pollutants such as fine particulate matter, sulphur dioxide, and nitrogen oxides. A specialized instrument (called a miniGC) can be placed in an Airpointer to measure volatile organic compounds, such as benzene, on an hourly basis. Airpointers differ from permanent monitoring stations in that they can be transported to other locations for temporary surveys (e.g. two weeks, six months, a year or longer).

Airpointers - air monitoring station

Passive Monitors

Passive monitors used throughout the CASA network are based on Environmental Protection Agency (EPA) Method 325, and are used for property line (fenceline) monitoring. Volatile organic compound (VOC) concentrations are measured using thermal desorption tubes packed with sorbent materials (Carbopack X).

Tubes are placed in outdoor shelters and are exposed to ambient air for a period of two weeks. Ambient VOCs diffuse to (move into) the sorbent material and are retained. The tubes are then sent to a laboratory for analysis, using gas chromatography/mass spectrometry, to quantify VOC concentrations over the two-week sampling period.

Passive Monitors - air monitoring station

Comparison of VOC Monitoring Equipment

As described above, there are several different types of VOC monitors that are used within the Sarnia air monitoring network. The table below compares how each monitor is used within the network.

Types of VOC Monitors

Non-Continuous Canisters

Real-Time GC

Airpointer MiniGC

Passive Monitor

Sample period





Sample Frequency

Every 6 or 12 days




Sample Analysis

Laboratory analysis required

Sample analyzed by monitor – results available in near real-time

Sample analyzed by monitor – post-processing of results required to determine concentration based on calibrations

Laboratory analysis required

VOC measured

>50 including benzene and 1,3-butadiene


Benzene, toluene, ethyl benzene, and xylene

Benzene or 1,3-butadiene



Christina Street

Front Street

River Bend

AP1 – Clearwater

AP2 – Eddings Street


AP1 – North Aamjiwnaang

AP2 – Vidal Street

Property-line monitoring as part of the Petroleum Refining and Petrochemical Industry Standards

Working towards improving Sarnia's air quality!