household dust is an odd combination of things- and having a dog certainly increases the 'dead skin' component of it. increasing the humidity in the room is the easiest way to cut down on airborne dust- it might also cure your cough (though if you're having any other breathing symptoms, or any swelling anywhere- get yourself checked for allergies. I'm an adult-onset dander, never USED to be allergic- but now the cat's not allowed in the bedrooms any more) the ionic and HEPA filter air cleaners WILL take out airborne dust- one of my clients has the 'smarter' ones in his house that needed cleaning EVERY DAY for the first few months he had it, and then it started catching up with itself, and now they get cleaned once a week, and even the plants look healthier.

Some of these comments are reiterated again and again. I am a retired HVAC/R professional with over 40 years experience. There is no cut and dried answer to most of these questions. Most of the answers are mostly correct in that you need to seal your ductwork, insulate it if it is in non-conditioned space (attic/crawl space), and the ductwork needs to be laid out correctly to supply AND return the correct amount of cfm to each room. After that, NO air conditioning technician in the world can correctly diagnose an air conditioner's problem unless several criteria are met. First and foremost, BOTH the condenser coil and the evaporator must be clean and the furnace (air handler) filter must be clean and not restricting flow. If you call a company out to your house and the technician comes up to your house with his gauges and refrigerant tank FIRST THING and immediately hooks the gauges up and starts putting refrigerant in, my advice is not to call that particular company back again. The coils MUST be clean before you can even begin to decide that the system is under or overcharged. Next you must make sure that you are moving the correct amount of cfm for the size air conditioner you have. 400 cfm/ton is the nominal amount for air conditioning. NOT ONE person has mentioned how important this is. On MANY occasions, I have seen brand new equipment installed and no one can figure out why it won't work! With brand new equipment, we know the coils are clean so that is not the problem. Let's say we have a house that is 2400 square feet and a new furnace and air conditioner are installed. It's a 105,000 btu furnace and a 3 ton unit. The homeowner complains that their old furnace and a/c (same size) worked fine until they had to have it replaced. Technician after technician comes out.....they hook up their gauges and add and remove refrigerant and can't figure out what the problem is. The a/c runs almost all the time and the pressures are correct but the relative humidity in the house is REALLY high and they can't figure it out. Some technicians recommend a whole house dehumidifier as a fix. C'mon people, let's not put a bandaid on this problem. What most technicians tend to forget with an installation of new equipment is that the new furnace doesn't KNOW what size air conditioner it is being mated with! The new furnace can typically be mated with (and has the blower assembly to work with) anywhere from a 3 ton to a 5 ton unit. These furnaces will have as many as 6 different speeds for the drive motor. A 5 speed motor is more typical but the factory sends these furnaces out USUALLY with the lowest speed set up for heat and the highest speed set up for cool. This means with the 3 ton unit (which needs 1200 cfm delivered), on the highest motor tap speed from the factory, the furnace is delivering 2000 cfm or more! Moving 2000 or more cfm through a 3 ton evaporator will result in a "delta T" of 10 degrees or less which explains the unit running almost continuously and the high relative humidity in the house. These technicians need to remember that they need to look in the installation manual to find the right motor tap speed to utilize with the size a/c being mated to the furnace. With the advent of the 95+ % furnaces, we are seeing ECM motors being deployed in the furnaces. These have no speed taps, but instead have a motor that is in essense a variable speed motor. The technician still needs to consult the installation manual as the motherboard in the furnace will have dip switches to set the motor drive unit to supply the desired cfm. Now, some "rules of thumb." IF your coils are clean, IF your furnace filter is not clogged up with dirt and providing a restriction, IF you are moving the correct amount of cfm for your size a/c, IF the superheat is correct and IF the subcooling is also correct, you should get a delta T of between 17-22 degrees and your supply temperature should be between 51-55 after the unit has run for 10 minutes or longer.

It could be that the supply box is not sealed to the floor, or ceiling..depending on where the supply air is located. Do you have condensation on the grills? Using a mastic tape to seal this junction will keep dust/insulation particles from entering the home. And is something that you can do from inside the home by removing the grill & sealing the box to the cut in the ceiling (or floor) with a mastic tape. I use Hardcast mastic tape. Often what happens is that when the grill is installed that the screws pick the supply box up..and particles & unconditioned air enters @ this area. Go into your attic..if the supply is in the ceiling & feel around the supply box. If you feel a gap between the box & ceiling..there is the entry of this unconditioned air. Best of luck & let us know what you find.

Were previous owners smokers? We redid a rental house & got new screens, 2 coats paint on each room, completely redid the kitchen, new cabinets, countertops, new appliances, light fixtures, etc. New floors & new carpet throughout. As we worked of course it was fall & had windows open. Right after realtor started showing the house to renters it got cold & we had to turn on heat, wow, did the house stink, we opened up that furnace door & it was dark dingy yellowed smoke, stale stink. so hours more of bleach water & cleaners before the place was pretty good. We added bowls of vinegar at night & hid them in the morning. by the time renters moved in it was pretty good. So try vinegar bowls where kids & critters can't get at them Open box of soda in closed in areas might help. Take a vent cover off & wipe out area of vent & rinse rag out in clean bowl of water, is it all brownish? Then it's probably the vents, if it is just dirty water with no smell that might not be it. I took a long skinny broom to couple of my vents a few times, got almost nothing out but I had gotten a high quality duck tape for attics & seams & so I guess nothing get in them to speak of. I have allergies big time, also clean out the area under furnace where air goes into to it from hall. I put a heavy piece of carpet pad that is covered with plastic on the floor under there & then wipe out couple of times a year by taking vent cover off. Of course no 1 smokes in my house but that area does get some dust. Yes fridge, freezers & humidifiers have drip pans that need cleaning or they can make you sick. Also if you have any drains that don't have water in the elbow sewer gas can come up & make you very sick, is there drain in center of basement floor- be sure to put gallon of water down it often or keep it covered, upstairs bathroom not used, get water in all the drains including tub or shower. Good Luck, Hope you find the problem soon.