The importance of using high-quality membrane filters

Portable air sensors can complement automated systems for roadside air monitoring. Learn the importance of using high-quality PM2.5 membrane filters.

The Clean Air Act

The United States Environmental Protection Agency (US EPA) takes the cleanliness of its country’s environment very seriously. Established in 1970, the agency’s sole purpose is to protect the public health of its citizens, by transforming the environmental laws passed by Congress, such as the Clean Air Act (CAA) into enforceable regulations. This act requires the EPA to set National Ambient Air Quality Standards (NAAQS) for six common air pollutants. One of these is particulate matter.

Air quality concerns

The level of particulate matter (PM) within the environment has been a primary concern of the EPA. The levels of fine inhalable particles with diameters up to 2.5 micrometers (PM2.5), are especially important, because they have been directly linked to the increased occurrence of cardiovascular and respiratory diseases, especially in older adults and children.

Roadside PM2.5 air monitoring

One of the main causes of these particles is traffic emissions. Every year, each state in the US must submit a Highway Performance Monitoring Systems report to the EPA, demonstrating that their PM 2.5 concentration is within the regulated range.

These reports are created using the data gathered from series of particulate tests performed by automated air monitoring devices, which are placed along a sample road segment within a state. The devices used in these tests are looked after by environmental engineers like Tyler.Tyler is a fictitious employee of a leading ambient air-sampling agency. This agency is hired by the EPA and local governments to track the annual levels of PM2.5 along Highway 7585 in the southeastern United States.

Automated filtration for continuous air monitoring

365 days a year, data will be taken from the group of automated air monitoring devices located at strategic spots along the highway. An air sample is drawn into the body of these devices, where it will be tested on a reel of filter paper using a beta ray. After a test is completed, another will take place —occurring continuously, every minute of every day.

Strategically placed portable air sensors

Tyler reviews the status of these devices every 3 months, deciding whether to service them or to check the accuracy of their tests. In either case, he will use a portable air monitoring device to work in its place or alongside it. These portable devices are stationed at the same strategic spots and will run for a period of 48 hours. These instruments will take in an air sample and push it through a 46.2 mm PTFE membrane filter – this test will happen continuously for this period. Afterwards, the filters are removed from the device and weighed to establish which particles have been captured.

Last week, one of Tyler’s continuous air monitoring machines broke down. Knowing that this would affect the flow of data to the EPA, Tyler rushes down with his portable device and a few packs of filters. When he gets to the highway, he notes that repairs on the machine have begun. Then, he sets up the portable device and reaches for the box of filters - upon opening the first box, he realizes that the all filters in the box are torn. He opens the next one, and half of the filters in this box are torn. Tyler isn’t happy, because this makes the tracking of each filter more difficult, potentially reducing the accuracy of each test. Reluctantly, he uses the torn filters, because he has no other choice.

In his next team meeting, Tyler explains what happened while he was in the field and asks his superiors if the department could start looking for another filter provider. He suggests using Cytiva’s Whatman PM2.5 46.2 mm PTFE membrane filter.

Whatman PTFE membrane filters

Tyler is aware that the Whatman PM2.5 46.2 mm PTFE membrane filter delivers the consistent quality that has been developed over the past 200 years. He also knows that these membranes are manufactured according to ISO 9001:2008 standards, and they meet requirements for the EM131.5 standard as well as the EPA’s reference method.

Made of PTFE, each filter is designed to be chemically resistant, protecting his samples from the environmental elements. And they provide more than 99% particle retention, ensuring that the right particulates are captured, which boosts the data accuracy of his portable device’s tests. Additionally, each filter is surrounded by a thermal resistance ring, reducing the possibility of filters curling and damaging his devices. More importantly, every filter is sequentially numbered, making it easier for Tyler and his team to track which filter was used during different sampling timepoints.

Tyler is currently using Cytiva’s Whatman PM 2.5 filters, and he couldn’t be happier.

For advice on filter material properties and compatibility, contact Cytiva support. Alternatively, use the filter selector tool to identify a suitable filter material for your application.