Answer: clean the exhaust vents and the air intakes with hot water, for the rest call a professional.
Regarding the gas CMV, there is the small maintenance that you can carry out by yourself, but a professional inspection is mandatory each year. All CMVs tend to clog over time, which is why it is necessary to regularly clean the exhaust vents and the air inlets, with hot water and washing up liquid (no detergents) . In the case of water-adjustable CMV, take care not to wet the fixed parts of the air inlets. However, certain parts of a gas CMV can only be serviced by a professional. The regulations in force require that a gas VMC be maintained by a specialized company, at least once a year for the verification of electrical conduits and connections. Once every five years to check the entire installation, in particular the safety device. Installing a window seal Our practical DIY videos