What about carpet cushion?

The cushion under your carpet is one of the most important considerations when buying new carpet. It is the base that helps the carpet retain its texture and appearance. A cushion is sold by its thickness and density. A pad that is too soft will adversely affect the performance of the carpet, and a pad that is too thick interferes with the anchoring of the carpet. For residential installation, a cushion of no more than 7/16-inch thick and no less than 1/4-inch thick with a 6 pound per cubic foot of density ...

I heard that new carpet can make people sick? Is this true?

According to the Environmental Protection Agency, like many other household products and furnishings, new carpet can be a source of chemical emissions. Carpet emits volatile organic compounds, as do products that accompany carpet installation such as adhesives and padding, and some people report symptoms such as eye, nose and throat irritation; headaches; skin irritations; shortness of breath or cough; and fatigue, which they may associate with new carpet installation. Carpet can also act as a "sink" for ch...