By Kim Smiley

Smoke drifting north from wildfires in Washington state has raised concerns about air quality in Calgary, but staff decided to check an air monitoring station after it reported an alarming rating of 28 on a 1-10 scale.  What they found was a bug, or rather a spider, in the system that was causing erroneously high readings.

The air monitoring station measures the amount of particulate matter in air by shining a beam of light through a sample of air.  The less light that makes it through the sample, the higher the number of particulates in the sample and the worse the quality of air.  You can see the problem that would arise if the beam of light was blocked by a spider.

This example is a great reminder not to rely solely on instrument readings.  Instruments are obviously useful tools, but the output should always be run through the common sense check.  Does it make sense that the air quality would be so far off the scale?  If there is any question about the accuracy of readings, the instrument should probably be checked because the unexpected sometimes happens.

In this case, inaccurate readings of 10+ were reported by both Environment Canada and Alberta Environment before the issue was discovered and the air quality rating was adjusted down to a 4.  Ideally, the inaccurate readings would have been identified prior to posting potentially alarming information on public websites.  The timing of the spider’s visit was unfortunate because it coincided with smoky conditions that made the problem more difficult to identify, but extremely high readings should be verified before making them public if at all possible.

Adding an additional verification step when there are very high readings prior to publicly posting the information could be a potential solution to reduce the risk of a similar problem recurring.  A second air monitoring station could be added to create a built-in double check because an error would be more obvious if the monitoring stations didn’t have similar readings.

Depending on how often insects and spiders crawl into the air monitoring equipment, the equipment itself could be modified to reduce the risk of a similar problem recurring in the future.

To view a Cause Map, a visual root cause analysis, of this issue, click on “Download PDF” above.