I am gonna guess that since you said it was wood, and plywood is the best choice for this application as it doesn't warp and crack in the same manner as solid wood boards and, it doesn't swell to 3X's its normal size when it gets wet like particle board or MDF that an assumption was made.
Particle board and MDF also off-gas formadahyde, ply wood may but in much smaller amounts as there is far less glue to give off the formaldahyde gases.
Although it is pricier I would suggest either X-PVC board or sheet ABS for durable easy to care for enclosures. Both can be chemically welded since few people have the forms industry uses to vacuum form components just laying around.