Smells From Next Door
A smell from the next suite is not coming through the concrete. It is coming through the openings in it, and there are more than anybody expects.
Short answer
Odour moves between suites through the exhaust riser, the corridor, plumbing and electrical penetrations, and the gap behind kitchen and bathroom cabinets. The direction is set by pressure, which is set by the building make-up air system and by what each suite is running. The fix is sealing plus correcting the pressure, not an air purifier.
The paths
The exhaust riser, where a shared shaft serves multiple suites and a suite with a stronger fan pushes into the shaft and across to another.
The corridor, where the building make-up air unit pressurizes the hall and air moves under the doors.
Plumbing and electrical penetrations through demising walls and floor slabs, which are rarely sealed.
The gap behind kitchen and bathroom cabinets, where the plumbing stack passes through and nothing is sealed around it.
Shared chases and the space behind a dropped ceiling or a bulkhead.
And the suite entry door, which is frequently the largest single opening when the weatherstripping has gone.
Pressure decides direction
Air moves from higher to lower pressure. A suite running a bathroom fan and a range hood with the windows shut is at negative pressure and pulls from its neighbours and the corridor. A building whose make-up air unit is off or unbalanced loses the corridor pressurization that was supposed to prevent exactly this, which is why these complaints cluster in buildings with a mechanical problem.
What an owner can do
Seal what is inside the suite: outlet and switch boxes on demising walls, the gap behind and under the kitchen and bathroom cabinets, the plumbing escutcheons under sinks.
Weatherstrip and sweep the entry door properly.
Clean the fan coil and change the filter, which is not the cause but affects what the suite air is like.
Avoid running the bathroom fan and the range hood together with everything shut, which maximizes the negative pressure.
Crack a window slightly when running a strong exhaust, which gives it make-up air from outside rather than from next door.
And report it in writing to the corporation, with dates and conditions, which is both the route to a fix and the record if it becomes a dispute.
What the corporation has to do
Check the make-up air unit is running and delivering what it should, which is the most common finding.
Check and balance the corridor pressurization.
Check the exhaust risers and the rooftop fans, and fit backdraft dampers where suites share a shaft without them.
Seal penetrations through demising walls and slabs during any work that opens them.
Address suite entry door weatherstripping as a building-wide item, which also helps with corridor noise and smoke.
And treat a cluster of complaints as a mechanical investigation rather than a neighbour dispute, because that is almost always what it is.
Common questions
Can smells come through concrete?
Through the holes cut in it, rather than the concrete. Sealing them is the fix.
Why does it come and go through the day?
Pressure changes with fans, dryers, weather and the building make-up air system.
Does a purifier in the suite help?
It handles particulate in your suite. It does not stop gases arriving.