Activated Carbon Diffusion
Diffusion Barrier Charcoal Canisters
AccuStar Labs - New England offers the RA40VCD diffusion barrier charcoal canister for your short-term radon testing needs. The diffusion barrier charcoal canister has been calibrated at our laboratory for a two to seven day exposure with a recommended exposure of three to five days. This canister design resists the effects of humidity allowing longer exposure times.
The canister is all metal of the Ellisco type of eight ounce capacity. The nominal dimensions of the canister are 4 inches in diameter and1 1/2 inches deep. The canister contains 70 +/- 1 grams of Calgon type 1193-coconut shell charcoal. The charcoal is 8 x 16 mesh and has a maximum radioactivity for gamma emitters of 0.2 pCi/g. The charcoal is held firmly in place by a screen of 30 - 50% openness and a borosilicate glass fiber filter with a basis weight of 22.9 grams / square meter. A polyethylene coated cellulose stock with 20 holes of 0.09-inch diameter provides the diffusion barrier. The screen and filter are held in place by an internally expandable ring of sufficient stiffness to hold the charcoal in place during handling including a drop from 3 - 4 feet onto a concrete floor. The canister is covered with a metal lid with a circular piece of foam material attached to the inner surface and sealed with vinyl tape.
Canisters are securely placed within a lead-shielded chamber in contact with a sodium iodide (NaI) crystal. The gamma radiation from the elements adsorbed onto the charcoal causes a light signal in the NaI crystal, which is electrically enhanced and counted using a ratemeter. Background counts are subtracted and the net counts are entered into a formula with other relevant data yielding quantitative results stated in picoCuries per Liter (pCi/L).
This device can be custom packaged for large project or individual use. Laboratory analysis and report are typically included. Single packaged tests kits contain one test canister and are best used as an initial screening test. Double test kits contain two test canisters and are designed to be used in real estate transactions following the EPA simultaneous testing protocol. They can also be used to measure the "stack effect" by placing one canister on the lowest level and another on a higher level. Bulk test canisters are available for use in testing large buildings and school.