An air cycle machine is the system that provides fresh, temperature-controlled oxygen to an airplane cabin. This complex machine avoids using freon-like air conditioning units and eliminates the moisture associated with those systems. It comes in different types, with each providing a different level of circulation. This machine is the industry standard for providing air to a cabin and has many other benefits, such as its reliability and environmental impact.

This machine begins its complex process at the engines. Bleed air is the excess air from these enormous turbines, and it is fed into a heat exchanger. The bleed air is too hot for comfort at this point, so the natural air temperature in the sky, usually hovering around the freezing mark, is used as a natural form of coolant. This air is sent to a centrifugal compressor in order to compress the air for efficiency purposes, but this also heats the air up again. The air once again passes through a cooling process using the outside temperature as it gets closer to being expelled inside the plane.

Very few individual spaces will exhibit identical thermal properties, so heat load calculations should ideally be made for each individual air conditioned area. Thermal load calculations may be done manually using tables of known values or by using heat load calculator software.

The thermal characteristics of any space are a complex combination of many factors. The location of the space, its use, the number of people who use it, and the number and type of appliances within the area all play a role. Seldom do two identical spaces, even if directly adjacent to each other, result in the same load. For instance, a bedroom housing three children each with their own computer will have a different heat load than the identical bedroom of a single young adult right next door. This would be particularly noticeable if one of the rooms received direct sunlight for most of the day.

A setback thermostat, also known as a programmable thermostat or a digital thermostat, is one way to promote energy efficiency in the home. The typical role of any thermostat is to regulate the indoor temperature by sensing changes and adjusting to the desired temperature. Users can program a setback thermostat with the specific times they want their heat or air conditioning to turn on and off. The term setback here also can refer to setting back the temperature to a lower one in winter or a higher one in summer. These adjustments can help conserve energy and save money.

If reducing heating costs and air conditioning costs is a high priority, then a setback thermostat might be a way to achieve that goal. Non-programmable thermostats usually remain on one temperature setting until they are manually changed. Many people think that maintaining a constant temperature by letting the heat or air conditioning run throughout the day is more economical than periodically changing the temperature setting. Yet most energy experts maintain that programmable thermostats often can save both money and energy by adjusting the temperature based on the time of day and who is at home.

Typically, new homes come with a setback thermostat already installed. Many of them include suggested settings programmed into the unit. These settings usually are intended to maximize energy efficiency and minimize costs by only heating or cooling the home at certain times. Consumers can follow the suggested time and temperature settings, or they can make adjustments to suit their own comfort levels. If someone has a non-programmable thermostat in his home and wants to upgrade, he could either do it himself or contact a trusted Heating, Ventilating, and Air Conditioning (HVAC) consultant to install a digital thermostat.

Vent covers are obviously constructed in a way that allows air to pass through them. Some are styled more like a grate, while others have louvers which can be adjusted to increase or decrease airflow, or to direct air to a certain part of the room. 

You may have heard of magnetic vent covers as well. These are used to cut off or limit airflow to certain spaces, and they are inexpensive and simple to use. They are made out of thin but sturdy magnetic sheeting, which can be cut down to fit any size vent. Since they are magnetic, they slip into place easily and stay there.

Magnetic covers also have another feature that makes them popular. They can be painted, wallpapered, and even covered with carpet so that they blend in and become virtually unnoticeable. To make standard vent covers blend in better, you can paint them the same tone as the floor, wall or ceiling.

Fan coil units may be more cost efficient than their air handling unit counterparts for a number of reasons. First, they are more financially feasible given that they need no ductwork installed to make them operational. They can also be installed in many different ways, such as horizontally using a ceiling mount or vertically using a floor mount.

An air filtration system removes pollutants from indoor air. Portable air filtration cleans the air in a single room instead of the entire house. Types of portable air filtration include HEPA air cleaners, ozone ionizers, negative air machines, and ultraviolet purifiers.

Electronic ionizers are another category of portable air filtration and are available in two types. Ozone ionizers work by creating an electrical charge that splits the air molecules. Some of those molecules then form O3, which is ozone. The ozone attaches to germs in the air, such as the germs that cause pneumonia, and also to viruses like chicken pox and Severe Acute Respiratory Syndrome (SARS). Though high amounts of ozone are a danger to humans, electronic ionizers only produce very small amounts and are only viable for about 20 minutes before converting back to normal oxygen.

Most dampers are also available with a manual operating option. They typically operate using a crank or switch located on the outside of the duct. Users must turn this crank to open or close the damper for both volume control and smoke control. While this option is simple and affordable, it may be impractical in emergency situations, when operators must activate the duct before exiting the building.

Cooling systems like fans, air conditioners, heat pumps and whole house fans are the primary methods of recirculating air, and they are implemented to make life more comfortable indoors. Each of these air circulation methods depend on moving parts to force the air to be expelled quickly throughout living quarters. 

During the hot summer months, it is the steadily moving air currents which provide relief from incessant sweating and dehydration, the two main forms of bodily discomfort. The added benefit of recirculating air also improves the atmosphere within the room through filtering the moving air, which helps trap allergens and particles.