There are many questions and even more misunderstandings around comfort and heat stress for people specifying or wearing arc rated and flame resistant protective apparel; thus, it is important to understand a few basics on the interrelationship, if any, to garment or fabric type and weight. Discomfort and heat stress are not used interchangeably. Comfort is an inherently subjective characteristic that cannot be effectively or predictably measured by lab tests or judged across a desk, and is considered a nuisance issue. However, heat illness is a specific and potentially medically consequential event; it is unrelated to comfort, and is a potentially major health issue.