Measuring radon is a relatively easy process but it should be carried out at a time that is best suited to being most effective. You don't want to be wasting your time, effort or money. The reporting requirements from Public Health England (PHE) include that measurements are "seasonally corrected". This is because temperature, humidity and air pressure all affect the within a structure. Validated laboratories (we use Radonova because it is a validated and accredited service)