Hypercapnia is an unusually high concentration of carbon dioxide in the blood which may be accompanied by hypoxemia, in which the oxygen level in the blood is low. This condition occurs as a result of poor gas exchange at the lungs which makes it difficult for people to eliminate carbon dioxide from their bodies.
Quick Answer. A tire treadwear rating refers to the amount of time the treads on a tire should last in specific conditions. Tire manufacturers indicate treadwear rating on their tires using a set of numbers between 100 and 700. These numbers indicate how long tire treads will remain safe and perform at their highest capacity.
You can make sure that the tread on your existing tires is safe by checking it at least once a month when you check your tires' air pressure. Start by culling out the riskiest rubber. Look for bald tires by checking whether any of the wear bars are flush with the tread's outer surface. Another way to check whether your vehicle's tires have reached their wear limit is to insert a penny into each groove, Lincoln's head down, as shown below. Replace the tire if the top of Abe's head becomes uncovered by any of the grooves.