Not all areas can be blocked or sealed with draught-proofing. Avoid blocking or sealing intentional ventilation. Some areas need air circulation to keep your house fresh and dry. Places like the kitchen and bathroom windows should have enough ventilation. Also, avoid blocking under-floor grilles, wall vents, and air vents for fires and heating appliances. For utmost safety, consult your draught-proofing expert or registered gas installer before your draught-proofing installation.