Q. I'm living in Shenzhen, People's Republic of China. I live on the 9th floor of our 34 floor apartment building, and just had to have our external air conditioning serviced. I was alarmed and amazed as our air conditioning technician tied a rope around himself, and then went out the window to the external air conditioning unit to give it a dose of freon (as I held the rope!). My gf asked, what do they do in the USA?

A. In the USA buildings have central Air-Conditioning and the equipment is usually located on the roof of the building.

Q. I just got the ducts in my house cleaned out to get rid of pet dander and help me breathe better. The air conditioning is running great now and seems cleaner to breathe in. The only problem is that there is a loud humming noise coming from the big vent on the wall. It only comes from this big vent, and does not resonate from any of the vents on the ground. The big vent is not the original big vent; my contractor replaced it after the ducts were cleaned because the old big vent was dirty. My contractor says the noise is a result of the air running so openly now, but I'm having a hard time buying that. I think it is the replacement vent vibrating when the air pushes through it. Any thoughts? I'm pretty sure he threw away the old big vent.

A. Call him back and tell him your not satisfied.Lining the duct with duct insulation should help.I think your right about the vibration.

Q. We desperately need an exhaust fan installed in our upstairs bathroom. There is one tiny window, which is not enough to expel all of the moisture (esp. living in FL!)... and no air conditioning vent. The bathroom is located on an exterior wall so I wouldn't think it would be too complicated. I just don't know who I should call to do it.

A. Actually, either one can do this job. When building new houses the electrician sets the fan housing and runs the wires, then the AC man runs the duct work when he roughs in his AC unit. Since there's gonna be a switch involved, I'd call an electrician first.

Q. The filter is completely frozen over with ice we cant even remove it.

A. Shut the AC off and let it defrost. Thats usually caused because the filter clogged from not being changed or cleaned. When the filter clogs, air can't circulate and the coils freeze up.

Q. I live in an upstairs condo. I have a small window air conditioning unit. I was going to install it on a shelf outside the window, but my guys said it is fine sitting on the window ledge backed up to the screen of the window and lowering the window down on top of it, as it has exhaust and intake. Any air conditioning experts out there who could tell me if this is a less efficient way for it to run, or is it all right?

A. Unless things have changed, the screen is approx. 3 to 4 inches from window sash ( the glass) the unit is about 14-16 inches deep. they r designed to sit flush to the sash with the upper arm( brace) touching the bottom of the sash u raised to put the unit in.and the slides on the side of the unit slide over to cover the gaps. i think u would be wise to read the instructions and follow them.

Q. In a 2400 sq. ft. house?

A. On the average $30.00 per vent plus a $40 set up fee per system price is usaully dictated by the numbers of vents in your house not the sqft

Q. The central air conditioning in my apartment is getting repaired and won't be working for 4 or 5 days. I want to improvise something. Maybe taking a fan and pointing it a a bag of ice. Heck.. I don't know... Any tips ?

A. Use the principle of evaporation. Depending on the humidity, it can work wonders. Lightly soak and wring out a sheet before bed, and have a fan blow across you. You will be comfortable enough to get to sleep. Some people get a large amount of ice, put it in a shallow pan, and have a fan blow over it. Another is to fill an ice chest with 70% ice and 30% water, take a hand towels, soak and wring out, then place over head and breathe the cold air. Do it once more but this time leave on your wrists for a couple of minutes. As for a whole house fix, there is no other DIY method I know of. The ice cold towel on the head is really amazing relief even though temporary.

Q. Please excuse my ignorance, but is there a portable air conditioning unit (blows out COOL AIR in a HOT ROOM) without being attached/fixed to the wall, as in carry it with you just plug it in to a wall socket and have it blow out cool air. I know this may seem like a dumb question, but a simple answer would be much appreciated. Thank you!

A. There are two units that are kind of like that, but not quite. one is called a swamp cooler. they evaporate water to absorb thermal energy in a room, but make the room more humid, and only really work in dry climates. however, they are relatively cheap to buy and use little energy. the other is a regular AC unit, but, this is not a window unit. they make one that is a free standing floor unit that can be pushed around and plugged in anywhere. however, the only downside is that there is a 3 or 4 Inch diameter hose that comes out of the back of the unit that must be run outside, through a window or a cat door or something. the unit is similar to window units in that it must move the heat from the room to the outside, but it does not have to hang out the window. they are about as expensive as regular window units. and are much more portable. you just have to point the hose outside. just remember, the heat has to go somewhere. it is very hard to just make it disappear (like an endothermic reaction, a reaction that takes heat)