It is an OSHA requirement to wear protective clothing when welding, cutting, or brazing.
OSHA 1910.252(b)(3) states:
Protective clothing – General requirements. Employees exposed to the hazards created by welding, cutting, or brazing operations shall be protected by personal protective equipment in accordance with the requirements of 1910.132. Appropriate protective clothing required for any welding operation will vary with the size, nature and location of the work to be performed.
And from 1910.132(c)
Design. All personal protective equipment shall be of safe design and construction for the work to be performed.
Here you’ll find a selection of welding apparel – jackets, bibs, aprons, sleeves, and pants made from various materials such as Kevlar, cotton, leather and pigskin – that will satisfy those requirements. Some of the brands include Tillman, Steiner, Stanco, and Cornwell to name a few.