In an air-handling system that provides cooled air to occupants of a building, most of the air is returned from the space back to the air handler to be reused. This is called â¦ Return Air, or RA. However, some fresh air (called Outside Air, or OA) must be mixed in.
Polio is a viral infection that can cause permanent paralysis. The inactivated poliovirus vaccine (IPV) is usually given at ages 2 months, 4 months, 6â18 months, and 4â6 years. Though the oral poliovirus vaccine (OPV) is still used in many parts of the world, it has not been used in the United States since 2000.
Most children get four doses of polio vaccine on this schedule: First dose when they are 2 months old. Second dose when they are 4 months old. Third dose when they are 6 to 18 months old.Last dose when they are 4 to 6 years old. Polio vaccine can be given as all shots (IPV), all drops (OPV), or a combination of both. vaccine is a medicine you take to keep you from getting a disease. The polio vaccine comes in two forms. Inactivated polio vaccine (called IPV) is given by injection (a âshotâ). Oral polio vaccine (called OPV) is given by drops in the mouth.