The 4 Pa test ensures that in case of low pressure (issued e.g. by a tumble drier or an extractor hood) no gases – like carbon monoxide (CO) – can penetrate into a living space. The low pressure limit values between outside air and living space are determined and documented over the time period of 5 minutes. They hereby should not exceed -by operating firing place and maximal suction performance- the limit value of 4 Pa (8-Pa test by heating plants independent from ambient air). The 4 Pa test can be performed with several ecom flue gas analysers or pressure meters.