Gas sampling systems or gas extraction systems were developed to detect toxic gases (poisonous gases) and flammable gases (explosive gases) from outside the danger zone. Air from the danger zone or a ventilation duct is led through a PVC pipe into the suction chamber, from where the gas sensor carries out the measurements. Depending on the application, the air can be pulled in by a fan integrated in the gas extraction system or taken directly from a ventilation duct without a fan. Gas sampling systems are often used for gases with a high density such as chlorine gas, sulfur dioxide, etc. These are very difficult to measure with conventional gas sensors.