If the house is under negative pressure, filters do nothing to stop dust.

Filters merely trap it so it doesn't clog up your HVAC system.

Negative pressure: pressure that sucks.

Positive pressure: pressure that blows.

Dust is everywhere you create it, your dogs, cats, if you smoke, if you scratch (dead skin cells, hair etc.) The more people in your household, the more pets, the more you smoke... the more dust and dirt you create.

Dust is also in the air outside... so if your house is under a negative pressure, it is sucking this dirty air into your home.

If your home is under positive pressure, dirty air from outside can not get in. But if you're a filthy animal... well? If the filter is dirty it's doing it's job...

I service the Katy, Texas area.

Well, but to the extent interior air is cycled through an HVAC system, filters DO remove particulates. If the particulates aren't there to clog up the HVAC system, they aren't there to get deposited on your piano. As far as I can tell, my house is under neither positive or negative pressure. Some pump would have to be creating that pressure, and I don't have any such pump. When I open a door, I don't feel air flowing in or out.

When I create dust, the only way that dust can get on my piano is if it's floating in the air. If it's floating in the air, it's going to go through my HVAC system. It's pretty well understood that HVAC filters are there at least partly to improve air quality in your home.

That being said, of course if you don't use an HVAC filter, your system will get clogged up.

"As far as I can tell, my house is under neither positive or negative pressure."

Nonsense!

Your forced air system takes a suction on portions of the house and returns air to other portions causing over pressure.

Sorry, but that results in moving air from one part of the house to the other. Higher pressure where it comes out, and lower pressure where it goes in. It doesn't involve net overpressure in the house.

I'll seek my answers elsewhere. Thanks!

"net overpressure" - So dust may come in the low pressure areas and some will go out int he overpressure" (sic) area for an over all net no dust? Moronic!

Bye, bye. Sorry we weren't smart enough to help you.

The issue is not where the dust comes from. It's how best to suppress it once it gets in.

Also, insults aren't cool, and they certainly don't help anyone. Why don't you chill.

Oh, I thought you said, "I'll seek my answers elsewhere."

I do wish you well with that1

Insults? Listen to yourself!

The issue is not where the dust comes from.

But it is.... because if you stop the flow of dust there is less dust to deal with.

When your HVAC system turns on, it naturally creates a suction.

When you do laundry and run your clothes drier... it creates a suction.

If you have a central vacuum. Same thing.

If you have powered attic fans that run. same thing.

Air out = air in

Air in = air out

If you turn on a fan... the air that is blown out from it? Where does it come from?

A fan does not "magically" create air. If the fan does not have the air it needs it sucks air from where ever it can get it. Thru sill plates in walls, thru electrical fixtures, thru light fixtures, thru windows, thru doors and door jambs etc.

The more powerful the blower / fan motor the more it's ability to suck.

Most homes have a single filter located centrally in the home, so your HVAC system turns on pulling dust from where ever it can, cycles off... the dust in that air then falls on your piano when the HVAC cycles off.

In 26 years of running HVAC service how many times you think I've seen this problem?

The question is how much money is worth it to fix it. It's either that or you break out the chocolate scented pledge every morning.

I service the Katy, Texas area.