Sealing gaps (and what never to seal)
Does sealing work? Yes. It slows how fast polluted air leaks in, which lets a purifier keep a room much cleaner. Here is where to seal and where not to.
Does sealing actually help?
Yes, as long as it is combined with filtration. Outdoor particles get into a closed room mainly through gaps around windows, doors, AC pipes and vents. Sealing cuts that infiltration, so:
- the purifier has less incoming pollution to remove, and the room settles at a lower level;
- the room stays cleaner longer if the purifier is off or slowed for sleep.
Sealing alone without a purifier helps less: particles still trickle in and nothing removes them. You can see the difference in the clean-room simulator.
Where to seal, roughly in order of payoff
| Gap | What to use |
|---|---|
| Gap under the door | Door sweep or a fabric draught stopper. Often one of the largest gaps in a room. |
| Sliding windows | Brush or wool-pile weatherstrip along the track and meeting rails. Close the latch fully. |
| Hinged windows and doors | Self-adhesive EPDM or silicone rubber “D” or “P” profile strip around the frame. Foam tape is cheaper but wears out faster. |
| AC pipe hole | Seal around the pipe with AC sealing putty or a suitable sealant. Never seal the drain line. |
| Unused exhaust fan or vent openings | A cover or a fan with a backdraft shutter. |
| Cracks in frames, gaps around fixtures | Silicone or acrylic sealant for permanent fixes. |
Renting? Removable weatherstrip, draught stoppers and putty come off without damage.
Never seal these
- Air supply for anything that burns fuel: gas geysers (water heaters), gas stoves, chimneys and flues. Blocking them can cause carbon monoxide poisoning, which can kill.
- Emergency exits, or anything that stops a window or door opening quickly in a fire.
- Bathroom and kitchen exhausts that vent to the outside. They remove moisture and cooking smoke.
- Drains and condensate lines.
Never burn charcoal, coal or wood in a closed room An angithi or sigri brought indoors for warmth, especially in a sealed room, can build up carbon monoxide to deadly levels while people sleep. Use an electric heater instead. A battery carbon monoxide alarm is cheap insurance in homes with any fuel-burning appliance.
Keep the room breathable
A well-sealed bedroom with two people sleeping in it will build up carbon dioxide and humidity overnight. That’s not a pollution risk, but it can cause stuffiness, headaches and condensation. Air the room briefly when the outdoor air is at its cleanest, or open the door to the rest of the (filtered) home in the morning. See ventilation.