With the 4-Pascal measurement, it is assured that air-suctioning systems (extractor hoods) - which share the same air space as a furnace - do not obstruct the chimney suction through the so-called stack effect.
This prevents flue gas from escaping into the environment and dangerous gas poisoning or carbon monoxide poisoning occurring. In the 4-Pascal test, an underpressure of at least 4 Pa is required.
4-Pascal measurement can be carried out efficiently with the flue gas detector Dräger FG7500.
The Pascal test starts with registration of the baseline. Then, all openings of the location are closed and then opened again three times, for 30 seconds each time.
If there are roller blinds on the window or the outer door of the display room, they must always be opened and closed. With closed openings (windows or doors), the underpressure and the clean extraction of the flue gases must be monitored. With open openings, the baseline must be reached again.
If the underpressure in the installation room of the furnace remains under 4 Pa. Or if the underpressure in tested room air-independent furnaces for solid fuels is under the maximally permissible underpressure of 8 Pa mentioned in the certificate of applicability.
Then you can be sure of the safe simultaneous operation of furnaces and air extraction systems. Of course, in case of a change in the furnace, a new assessment must be carried on the other influencing devices or the building.
Sanitary, heating, and air conditioning professionals, heating engineers, installers, and chimneysweeps use the 4-Pascal test every day.