Ambient Air Monitoring

Ambient Air Monitoring for Benzene at Corunna Site

Collecting the Data

The air monitoring program assesses annual ambient benzene concentrations along the Corunna facility’s perimeter using passive diffusive monitoring technology that has been approved by the Ministry of Environment, Conservation and Parks (MECP).

Samples are taken continuously over a two-week period according to a plan approved by the MECP.

Corunna Site Ambient Monitoring Map

UPDATED: September 24, 2019

Corunna Site Ambient Monitoring Map


Results are then posted (see below) within 60 days of sample collection in order to comply with the Standard.

Corunna Site Ambient Monitoring Data – Benzene

UPDATED: June 18, 2024

Corunna Site Ambient Monitoring Data – Benzene


Establishing a Baseline

Following three full calendar years of monitoring, a three-year benzene measurement baseline will be determined for each monitoring location. The baseline will then be updated annually based on the measurements from the previous three calendar years.

Assessment of Results

Results are influenced by many factors, including:

  • Wind direction and speed
  • Ambient air temperature
  • Proximity of monitor to on-site sources of benzene
  • Proximity of monitor to off-site sources of benzene

Because of these factors, results can fluctuate – between each monitoring event at the same, or different, monitoring locations.

The two-week monitoring results serve as a means to calculate a baseline, an annual average benzene concentration and to compare annual measurements to the established baseline. The two-week results are not intended to be assessed in isolation from annual or baseline data sets.

Following the fourth year of monitoring, a statistical comparison to the baseline will be performed for each monitor based on measurements from the previous calendar year. If there is any location with a statistically significant increase from the baseline, further analysis will be conducted to assess for potential actions to prevent, minimize or reduce the risk of future statistically significant increases in annual benzene concentrations.

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