Airborne particles come from many different sources, such as smoke, sea salts, suspended soil, photochemical reactions and natural particle emissions. These aerosols affect visibility, climate and human health. Therefore, monitoring aerosols is essential to maintaining our quality of life.
Filtration and impaction are two methods of aerosol collection. Filtration occurs when the aerosol passes through filter media. Aerosol impaction occurs when an airstream is focused onto a perpendicular surface. Particles above a certain size impact because their inertial forces are strong enough to overcome the drag force of the airstream.
Aerosol Impaction has several advantages:
- Aerosols may be segregated into sizes (filters only have one size)
- Aerosol samples are better preserved (during particle impaction, the airflow moves over the sample, and provides less desiccation and chemical transformation)
- A variety of impaction surfaces may be used (most common media are Mylar, PTFE, and Aluminum)
- An impaction sampler may operate unattended for several weeks, without the need to change filters (a single DRUM collects over 2500 unique samples in a single deployment)
Photo: A six-week continuous DRUM sample of particles between 0.09 and .26 um. (Our DA800 DRUM sample has 8 drum disks that operate simultaneously, each disk calibrated to specific particle sizes)