The working level unit is used to determine combined alpha radiation from all radon decay items. Industrial test packages designed for use by the public are widely available. The most usual kinds consist of the use of charcoal containers, alpha track detectors, liquid scintillation detectors, and also ion chamber detectors. The examinations are typically made to be returned to a certified research laboratory for evaluation. The EPA approximates that virtually one out 15 homes in the United States has raised radon levels.