Get a dog or a cat, and within 60 days your indoor air has fundamentally changed. By year two, the duct system is a measurably different environment. By year five, if nothing has been done about it, you are running an HVAC system whose interior is coated in protein.
This isn't a criticism of pet ownership. It's a physics problem.
Why dander is different from dust
Normal household dust is mostly fiber, paper, dead skin, and exterior particulates. It's inert — it settles, it can be vacuumed, it doesn't really change chemically once it's deposited.
Pet dander is different. It's largely protein — specifically, Fel d 1 from cats and Can f 1 from dogs. Proteins are biologically active. They re-suspend easily, they bind to upholstery and duct interiors, and they provoke immune responses in sensitive people for years after the pet itself has gone.
This is why you can walk into a house that had a cat fifteen years ago and still feel your eyes itch. The dander is still in the ductwork.
The compounding problem
Filters catch particulates that are big enough. Dander has a wide size distribution — some of it is large enough to be caught by any MERV 8+ filter; a meaningful fraction is fine enough to pass through everything below a HEPA-grade filter (which most residential HVAC systems are not designed to accept without modification).
The fraction that passes through the filter settles on the duct interior. The next cycle picks some of it back up and redistributes it. Over months and years, the duct interior becomes a secondary reservoir — not as bad as the original source, but continuously re-emitting.
What to do
If you've had pets in your home for 2+ years and the ducts have never been professionally cleaned:
- Book a full duct cleaning ($399). This is a one-time reset — it removes the reservoir. Budget another $349 for a UV light install if any family member is reactive.
- Upgrade your filter to MERV 11 and change it every 60 days (pets accelerate filter load significantly).
- Consider sealing any return-side leaks. Unsealed returns pull dander-laden air from attic, crawlspace, or wall cavities back through the system.
How often to repeat
For active pet households, we recommend a professional duct clean every 2–3 years instead of the 3–5 year interval for pet-free homes. Filter changes every 60 days, not 90. Nothing else changes.
If you also have a fireplace, stack the chimney sweep onto the same visit — dander plus creosote is a worse combination than either alone, and the bundle rate makes it $169 instead of $249 booked separately.
Book a full duct clean or call (408) 655-0609.