Start with the HVAC problem
Dust around a register is not the same as evidence that an entire duct system needs cleaning.
Filter and system maintenance matter
Use furnace/air-handler filters and service schedules appropriate to the equipment.
Get a clear scope
If hiring a duct cleaner, ask what parts of the system are included and what evidence supports the work.
Avoid health guarantees
A duct-cleaning company should not promise to cure medical conditions.
General consumer information only. Do not mix cleaning chemicals or improvise electrical, chimney, high-access, pressurized, drain or other safety-critical work. Follow Canadian product labels, recall notices and the exact manufacturer’s instructions.