Radon in air test kits include two radon sampling test canisters, instructions for use, data sheet for notation of exposure information, a pre-paid return mailer and a pre-paid report of laboratory analysis. Designed to be used in real estate transactions following the US 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. Each test canister is an open face activated charcoal canister measuring 4 in. Dia, 1 in. D, and contains 75 g of activated charcoal. The devices are designed to be exposed in an indoor environment for a minimum of 48 hours and a maximum of 96 hours, with a recommended exposure of 48 hours. To begin the radon measurement the user removes the tape and the lid and sets the canister in a room for the chosen exposure period. The user writes the start date and time, ending date and time and test location information on a data sheet. During the exposure period the device is left open and undisturbed, so that radon-laden air can diffuse through the metal screen and adsorb onto the activated charcoal. In the laboratory, the closed device is placed on a gamma detector. The average radon concentration over the exposure period is reported in picoCuries per liter.