He has the right to refuse any job that he feels is unsafe for HIM...with out repercussion ...everyones tolence is different when it comes to anxiety ,temperatures noise tolerances...so there is no specific levels...its up to the person that has to do the task under any circumstances or conditions what their levels are....I am IAPA certified and OHSA certified...
Better question is ...why would an employer want to put his equipment/employee at unnessasary risk of being damaged or lost...
Hope it helps...