Rubber is the most commonly used materials and is an inexpensive choice (in comparison to other materials) for air and gas pipes. These pipes are strong, flexible, durable and can handle different heat and temperature variations. Rubber compounds like EPDM and NBR also make a great choice for air and gas pipes. EPDM rubber provides great resistance with heat, temperature and ozone. Similarly, NBR is resistant to oil and chemicals. However, rubber cannot provide zero permeability and cannot be used for applications which requires high purity. A high purity gas has low amount of other gases present, making them better quality. Permeable materials may compromise the quality of such gases by picking up contaminants.