Depending on the combustion air supply and the flue gases, the gas appliances are divided into three basic categories. Appliances in category A have air intake and flue gas directly into the room where they are installed. Typically it is a gas stove. Category B appliances have air intake from the surrounding area, but flue gas outlet opens into the chimney. These are, for example, older gas flow heaters. Modern appliances in category C use the air supply and the flue outlet outside the building - for example through the outside wall of the house or the chimney.
"In terms of possible flue gas penetration into the interior and the risk of carbon monoxide poisoning, the most problematic gas appliances of category B are . It is because they can easily penetrate the flue gas in the interior due to poor installation. Conversely, in the case of modern category C appliances, these problems are hardly on their way, " says Roman Švantner (ENBRA).
It depends on air access to the installation room
To prevent the passage of flue gases, sufficient air supply must be provided to the room where the B-type gas appliance is installed. The amount of air flowing into the room must correspond to the exhaust gas flow into the chimney. "If the air supply is not sufficient for the chimney drain, a negative pressure will be generated at the appliance location, which will act against chimney draft. The flue gas can thus gradually penetrate the interior. This can be done in bathrooms with well-sealed windows and doors, "said Roman Švantner.
Improved air access to a room with a Category B gas appliance will mainly help the various ventilation flaps, door vents and ventilation slots in the windows. These will ensure a steady access to the air without too much cooling of the room.
Beware of hoods and fans
A big risk is also dragging the flue gas into the interior due to low room air pressure or high draft. For example, the cooker hood is in the kitchen. It can cause vacuum in the rooms to overcome the draft of the chimney, and the flue gases begin to penetrate into the interior. The same problem may arise, for example, with a fan, a central vacuum cleaner or a strong draft due to the open door to the staircase. The solution is consultation with a specialist, a careful inspection of the appliance's location, risk assessment and measurement of flue gas draft in the chimney.
Do not underestimate the technical condition of the appliances and modernize them
The technical state of the gas appliance is also significantly influenced by its safe operation. A clogged and uncontrolled exchanger may cause incomplete combustion and therefore the production of hazardous carbon monoxide. As a matter of course, annual inspection of gas appliances should be an expert, even though the Act does not explicitly regulate it to households. It is also worthwhile replacing old gas appliances with more modern ones. They offer not only safer, but usually much more efficient, traffic.
Source: tz, edited editorially