Before deciding to buy an air conditioner or air purifier, you have to carry out a detailed study of your home. It is important to know the square footage of the rooms you want to air condition, and how high the ceilings are. You should also check how many windows the room has and make sure they close properly to insulate the room.

It is also important to know which way the home faces because those facing south and west are much hotter. Finally, if you home is a penthouse or on the top floor you need to know you will need greater cooling power.

Power is measured in British thermal units or BTUs. A BTU is a unit to measure heat absorption, which is used in refrigeration. It corresponds to the absorption of one kilocalorie. To do your own calculations, in a room of between 10 and 12 square meters, a 3,000 BTU unit will suffice. For the rest of the rooms, it is easy. If the room is bigger you will need more BTUs and vice versa.

Air conditioning
These are the most popular, and have evolved a lot, especially with regard to noise because now they are much more quiet. These days you can buy air conditioning systems that cool in the summer and heat in winter (so-called heat pumps).They can be installed pretty much anywhere in the home, but need an exterior outlet for the flexible tube used to expel condensed water. If you want to place many units outside, you can have the tubes from the interior units converge in the same outdoor unit. The principle maintenance task is to clean the filters about every six months.

Air purifiers and other devices
But if what you prefer is not just cool air but clean air, you can buy air purifiers. They feature oxygen generators which have a small inner membrane that traps nitrogen in the air and releases a high concentration of oxygen.

These devices also usually have negative ion generators. These are molecules that have gained one electron. Pollution in big cities causes many positive ions to accumulate in the air. But the ions that are healthy are the negative ones because they freshen the air and help prevent headaches, irritability, overall discomfort and anxiety.

Basic tips
Once you have made your choice, keep in mind a series of rules applicable to all cooling systems so that you use them properly:
- The ideal temperature for your home is between 20 and 25�. This way you will avoid heat flashes when you leave the house.
- The stream of cool air should never be directed at people or pets. Point it at the ceiling or some considerable height. 
- If you want to save on your monthly bill, make sure the windows and doors of the air conditioned room are closed.
- Once every six months or once a year �depending on which system you have� you should clean the air filters.