UN Thread Types. UN (Unified) is a specification of the shape and dimensions of the thread for a given size (diameter) of fastener and number of threads per inch of fastener length. UN bolts and machine screws are the type of fastener in everyday use in the US, UK, and Canada. UN, UNR, and UNJ thread dimensions are measured in Imperial units.
Causes The airway can become narrowed or blocked due to many causes, including: Allergic reactions in which the trachea or throat swell closed, including allergic reactions to a bee sting, peanuts, antibiotics (such as penicillin), and blood pressure medicines (such as ACE inhibitors) Chemical burns and reactions. Epiglottitis (infection of the structure separating the trachea from the esophagus)
Tracheitis (Inflamed Windpipe) Causes, Symptoms, Treatment. The trachea or windpipe is a small tube, which connects the voice box or larynx to the lungs and provides an air passage. Some time the inner lining of the trachea in the humans can get inflamed and this condition is called tracheitis. Various bacterial infections can lead to tracheitis; however, tracheitis can also be caused by some other infectious and non-infectious factors.