An isolation room is a specially constructed area in a hospital designed for housing patients with an infectious disease in order to prevent the spread of the disease in the hospital. Unlike a clean room, which is designed to isolate the outside from the patient, the isolation room is designed to isolate the patient from the rest of the world. Thus, although they share important similarities, they are not interchangeable. For example, a clean room has to be made out of primarily hypoallergenic materials, while an isolation room must be designed with antiseptic principles in mind.
As many diseases can be spread by aerosol droplets, containing the air in an isolation room is of critical importance. However, the room cannot be vented either to the hospital or the outside air without filtration, although (unlike a clean room) outside air may be allowed in. As such, isolation rooms are generally kept under pressure than is lower than ordinary air pressure to allow air to only enter the room. In fact, it is bad protocol to make the room sealed - air should always be flowing into the room through the bottom of the door so this can be monitored to show the room is working as intended. The air in an isolation room is generally changed at least six times an hour. This allows the air to be constantly cleaned of pathogens.
Another important matter is staff training, and generally only specially trained staff is allowed in an isolation room - visitors are strictly excluded. Staff must go through a decontamination protocol every time they leave the room to prevent pathogens leaving on skin or clothing.
A set of isolation rooms is shown in A Pox on Our House.