A short-term air sampling effort from a natural gas compressor that was conducted in July by the Pennsylvania Department of Protection (DEP) found no air emission levels that would pose a health concern, contrary to concerns raised earlier this year by the state’s Clean Air Council (CAC).

The DEP’s results, issued Thursday, detailed sample monitoring that was conducted near Chief Gathering LLC’s Barto Compressor Station in Lycoming County. Philadelphia-based CAC had reported in January that Barto’s emissions posed health concerns because of high nitrogen dioxide (NO2) levels, and DEP conducted the sample monitoring in July.

Barto, located in Penn Township, consists of nine gas-fired internal combustion engines that move up to 150 MMcf/d of natural gas in the Marcellus Shale.

CAC had monitored Barto’s NO2 impacts using the best technology available and then compared the results against the federal one-hour NO2 national ambient air quality standards, set at 100 parts/billion by the U.S. Environmental Protection Agency. It found the NO2 levels were “very significant” because the emissions alone exceeded the federal standard.

DEP results were the opposite. Over a four-day period in July, an air sampling effort measured nitrogen oxide (NOx) levels near the compressor station while it was operating at “normal” capacity. A mobile laboratory was set up and equipment was placed within one-half mile downwind of the station at two different locations. The operator was not contacted about the sampling until it was completed, regulators said.

DEP’s results indicated that NOx concentrations “were minimal and well below national ambient quality standards.”

State environmental regulators operate permanent NOx monitors downwind of other compressor stations in Pennsylvania, and “those monitors are also measuring levels of this pollutant that are well below the national ambient air quality standard,” DEP said. “Three short-term ambient air quality monitoring studies have been conducted in drilling regions of the state, all of which detected no levels of any pollutant that would violate federal ambient air quality standards or pose a health concern,” said officials.

The stark contrast in CAC’s monitoring and DEP’s sampling is being reviewed, according to DEP. “DEP is committed to understanding the impacts of the natural gas industry on public health and the environment,” Acting DEP Secretary Chris Abruzzo said. “We will continue to conduct air sampling studies to ensure the quality of Pennsylvania’s air and the protection of its citizens while this clean, domestic fuel source is being developed, processed and used.”

DEP expects to complete by the end of the year a long-term study in Washington County to collect data for ground-level ozone, particulate matter, carbon monoxide, NOx, hydrogen sulfide, methane and volatile organic compounds. To review DEP and CAC reports, visit www.dep.state.pa.us and click “Air.”