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.
Four doses of polio vaccine (IPV) are routinely recommended for U.S. children at ages 2 months, 4 months, 6-18 months, and 4-6 years. The first dose may be given as early as age 6 weeks..S. residents 18 years and older generally do not require polio vaccination. However, in this case the person is required to have evidence of vaccination for a medical training program. People who receive a mixed series of OPV and IPV should receive a total of 4 doses.