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.
Article Body. Most of the vaccines your child receives are given by shots. One can be given in a nasal spray (a version of the influenza vaccine). In the past, the polio vaccine was placed on a sugar cube and given by mouth (this form of the polio vaccine is no longer available in the United States). But no matter how they are given, the general ideas of the vaccines are all the same. To help you understand how immunizations work, hereâs a little background on the bodyâs immune system and the way it functions. When your child becomes infected, his body relies on his immune system to fight the invading organism.