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Liberty Air Quality Monitor Experiences Malfunction; GASP, ACHD Provide Answers

Updated: Jun 11

At GASP we review air quality data the Allegheny County Health Department (ACHD) publishes on a regular basis. Today we noticed previously published data disappear from ACHD’s Daily Summary report. This is an issue that happens from time to time and wanted to take time to explain if you’ve ever noticed a similar phenomenon.

This particular case started Tuesday morning when GASP staff reviewed the hourly air quality data ACHD publishes on its website here. The report page showing data from the Liberty monitor on Oct. 25 appeared as we’d expect: full of numbers. 

But when we checked the same report today, the Oct. 25 entries (as well as entries from Oct. 23, 24, and part of the Oct. 26) for H2S and SO2 were replaced with a letter “C” or “I”.

We asked ACHD for an explanation. Credit to them for a quick response:

“Yesterday one of our engineers on the monitoring team fixed [a monitor malfunction] and today we are doing diagnostic testing to confirm that it is running correctly again. The monitoring team invalidated all the hours affected by the malfunction; these hours are marked “I” in the daily summary. After the diagnostic testing today, we will update the data over the past 24 hours if needed.”

Of course, glitches happen, and we are glad to see ACHD take seriously the job of ensuring that only accurate, vetted data are published. In fact, this is a distinct benefit of having regular, required monitor maintenance. When questions arise about specific data, there is an agency required to comply with federal monitoring standards and keep related records.

In this case, specifically, the timing of the malfunction was inopportune: Hydrogen sulfide levels at North Braddock exceeded the Pennsylvania 24-hour standard on Oct. 25, which makes H2S levels at Liberty a topic of great interest. But as we said above, GASP looks at ACHD monitoring data regularly and these issues happen at what could be characterized as both consequential and inconsequential moments.

Going forward we hope ACHD will continue to be open and transparent in communications about these issues when they arise.

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