Answer to Question #5701 Submitted to "Ask the Experts"

I am trying to find a commercial source for an air-sampling device called a diffusion screen or diffusion battery. They have been used to sample radon and other isotopes attached to ultrafine particles.

The effectiveness of radon decay products to deliver dose to lung tissues depends on the size of the decay product. Shortly after they are created, these particles are quite small (~1 nm) and highly mobile. As they age they may aggregate with more atoms from the air and attach themselves to an existing aerosol, growing to as much as 1,000 nm in size. Diffusion battery devices separate radon decay products into size fractions using differential mobility to capture the higher-mobility particles. Often these devices draw the air sample through one or more fine mesh screens that precede a "collect-all" filter.

Commercially available examples of devices that separate the highly mobile nanoparticles from the rest are the SARAD EQF3120, a continuous sampling electronic monitor, and the Rad Elec E-RIPSU, an integrating monitor.

If you want to parse the airborne radon decay products into more than two size fractions, you need a multiple-size fraction instrument.

Daniel J. Steck, PhD