Last November when we moved into our house, we turned the heat on and noticed a really musky, basement like smell and also dirt. We thought it'd just wear off after a while since it was the first time turning it on but it still smelled. We also had a lot of nasal/sinus problems but we always have those so I'm not sure if there is any relation. Well, we have our AC on now and it is just as bad. It's hard to sleep at night because it just feels like you're breathing in dirt and it really irritates our throats. It's just so musky smelling and we've noticed that the house is REALLY dusty. I'll dust in the afternoon and by the next morning everything needs to be dusted again. The smell goes away when the heat/AC is off except in the bathroom. In the bathroom against one wall, there is still a musky smell. But on the other side of that wall is the furnace.
We also have to run a de-humidifier constantly or we have what looks like water drippings on our walls.
Someone is coming to look at the furnace this week to see if that's the problem.
What do you guys think? Is it mold? Dirty air ducts? Can mold be inside the furnace or air ducts?

First make sure you check all your filters and replace them if in doubt it is cheap insurance. If it gets dirty in there it is likley due to mold spores growing in your ducting and vent pipes. This can be very dangerous IF you have allergic reactions. You need to have your vent work cleaned or youcan checke to see if you have mold by doing it yourself. The best way is to pull some of the vents and run a duster in the vent. If you pull it out you will be able to tell if you have mold. Mold is nold and looks well... like mold... If you find mold then it is usually completely through out the system. Then you will need to get it cleaned and I would suggest professionally or go to the local Home Depot and they do make kits to do it yourself.
Keep us posted on how things go...

Actually what you need to do is have your Coil for the A/C unit cleaned. A/C coils can also cause a dirty sock smell that is close to what mold can smell like. Ben in the HVAC trades for over 35 years and I bet it is the coil and pan assembly is dirty. Mold in the duct is also possible but it usually starts at the coil because mold needs moisture and the only moisture in a HVAC unit is located at the A/C evaporator coil. Depending upon your skill level you might have to get a pro to do this for you. They have special cleaners that are safe for indoor use. NOTE No acid based cleaners allowed in the house. That cleaner is for outdoor use only.

Actually what you need to do is have your Coil for the A/C unit cleaned. A/C coils can also cause a dirty sock smell that is close to what mold can smell like. Ben in the HVAC trades for over 35 years and I bet it is the coil and pan assembly is dirty. Mold in the duct is also possible but it usually starts at the coil because mold needs moisture and the only moisture in a HVAC unit is located at the A/C evaporator coil. Depending upon your skill level you might have to get a pro to do this for you. They have special cleaners that are safe for indoor use. NOTE No acid based cleaners allowed in the house. That cleaner is for outdoor use only.

Thank you! We have someone coming out to look at it this weekend. I'm a 19 year old female so I have no idea about furnaces! But I was thinking it was the coil too after doing a little research online.
Do you know why we would have problems with the water dripping on the walls during the winter when the heat is on? That is normally when we have to run the de-humidifier.

Thanks for your help!

Water is caused by moisture in the air. If your furnace has a humidfier it could be the cause. While the service person is looking at your a/c coil have them check the other water problem and the possible cause also.

Last November when we moved into our house, we turned the heat on and noticed a really musky, basement like smell and also dirt. We thought it'd just wear off after a while since it was the first time turning it on but it still smelled. We also had a lot of nasal/sinus problems but we always have those so I'm not sure if there is any relation. Well, we have our AC on now and it is just as bad. It's hard to sleep at night because it just feels like you're breathing in dirt and it really irritates our throats. It's just so musky smelling and we've noticed that the house is REALLY dusty. I'll dust in the afternoon and by the next morning everything needs to be dusted again. The smell goes away when the heat/AC is off except in the bathroom. In the bathroom against one wall, there is still a musky smell. But on the other side of that wall is the furnace.
We also have to run a de-humidifier constantly or we have what looks like water drippings on our walls.
Someone is coming to look at the furnace this week to see if that's the problem.
What do you guys think? Is it mold? Dirty air ducts? Can mold be inside the furnace or air ducts??
rockexrolloh, I am new to this site and maybe too late to help but I wanted to try. I am an HVACR contractor and a home science specialist. Your problem in your home could become a serious problem if not properly dealt with. You need someone with the proper training and testing equipment to find and solve this problem. I would need more information to be of much help to you by e-mail but you should go to Comfort Institute: Helping homeowners acheive a safe, healthy, clean, comfortable and affordable indoor living environment (http://www.comfortinstitute.org) and find a member in your area. I would be more then happy to help you further if you need me to. Whatever you do please make sure you get this resolved.

Bramsey 7 made you a nice offer for help. On other thing I might ad to this is make sure the furnace man checks your furnace for a defective heat exchanger. The symptoms of water on the walls and the smell can be a cracked or burnt out heat exchanger this is very important. They should use a digital tool Or a Kane May tester or another tester that is certified for this use.

Do not let them just do a visual check or a smoke test because most of the time those kind of test will not find the problem. The items you describe could also be the symptoms of CO poisoning and that can and will kill you in a high enough concentration.

THis type of heat exchanger failure in a hot air furnace is more common than most people know. Many people loose there life every year to Carbon Monoxide poisoning.