A company-provided vest with your name-tag and pin required. No leggings, jeans are okay. No logos on shirts, plain/patterned tees with sleeves only. No sleeveless tops allowed. Sometimes dress-up for holidays/events as long as health/safety policies aren't broken (EG long necklaces are dangerous as you're up-and-down ladders a lot).
Casual, though there was an employee vest we had to wear.