A check valve, clack valve, non-return valve or one-way valve is a valve that normally allows fluid (liquid or gas) to flow through it in only one direction. Check valves are two-port valves, meaning they have two openings in the body, one for fluid to enter and the other for fluid to leave.
Some causes of cold intolerance are: 1  Anemia. 2  Anorexia nervosa. 3  Blood vessel problems, such as Raynaud phenomenon.  Chronic severe 1  illness. General poor health.  Underactive thyroid 1  (hypothyroidism) Problem with the hypothalamus (a part of the brain that controls many body functions, including body temperature)
How Long Do Colds Last â¦ and How Can You Make Your Cold Go Away Faster? Most uncomplicated colds last between eight and nine days, but about 25 percent last two weeks, and five to 10 percent last three weeks. Even the most stubborn colds will typically resolve in a few weeks' time; this is actually one of the ways you can distinguish a cold from allergies.