Below is the wording from the document at left, which is the installation sheet about fire pits that Trex prepared for contractors and homeowners that install Trex decking:
Outdoor fire pits and fireplace use with Trex:
There are several factors to consider when using fire pits and fireplaces in conjunction with Trex decking. Most notably is the whether the fire will be gas or wood burning. Trex decking will soften as low as 176 degrees Fahrenheit.
Most of the fire pits in Trex ads that show a fire pit are gas burning. In this case the fire pit is installed by cutting around the Trex decking. The fire pit is not installed on top of the Trex decking. A fire-resistant material is installed under the fire pit and a protective “wall” made of stone or other fire resistant material is installed to hold the fire pit in place and also to protect the decking from heat.
Wood burning fire pits are not recommended on top of Trex decking unless using a product called DeckProtect™. Wood burning fire pits can damage the decking due to the extreme heat from the bottom of the fire pit and/or burning embers “shooting” onto the decking. DeckProtect™ was tested on all Trex decking and there were no issues with burning of the decking surface when placed directly under a standard size portable fire pit along with the accompanying rack (check with manufacturer to determine size that would be needed). Trex does recommend that the DeckProtect™ padding/rack be moved from time to time for general cleaning underneath. For more information about this product please visit their website at www.deckprotect.net.
It should be noted that even when using DeckProtect™, burning embers could “shoot” beyond the protective mat and burn the deck.
Trex Technical Services