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.
In the U.S., all infants and children should receive 4 doses of inactivated poliovirus vaccine (IPV, Sanofi) at ages 2, 4, and 618 months, and 46 years. The final dose should be administered at age 4 years or older, regardless of the number of previous doses, and should be given 6 months or more after the previous dose.