Class A chimneys are insulated to prevent the outside of the chimney from becoming excessively hot. There are two types of insulation used: packed pipes and air insulated pipes. Packed pipes have a double wall with insulation between the layers to help absorb the heat.

What is Type A chimney pipe?

Class A chimney pipe has many names, often referred to as double-wall chimney pipe, triple-wall chimney pipe, all-fuel pipe, or insulated chimney pipe. Class A pipe is used to vent high-temperature exhaust released from wood, coal, and oil-burning appliances such as fireplaces, stoves, boilers, and furnaces.

How hot does Class A chimney get?

This standard, which is known as UL 103 mandates that Class A chimneys be designed to operate at a continuous temperature of 1,000 degrees Fahrenheit.