Because all treadmill mats are made differently, some treadmill mats may be made of toxic materials. Many of these materials are usually only toxic if ingested, which makes them dangerous to pets or children with a habit of biting or chewing on inedible objects. Some mats also release VOCs when first opened which can be toxic in high quantities. It is important to air out your treadmill mat for a few hours outside once you remove it from the box. However, some treadmill mats are entirely nontoxic, which are a great choice for fitness fans with children or pets.