In a way, you just answered your own question. Get a copy of the health and safety regulations the workers must follow. Talk and write about it in a way that they can actually understand. Have the students show you what good procedures are (e.g., lift heavy boxes from the knees, not the back). You can use that to practice both simple present and present continuous. (I always put in my earplugs when I use the machine; I am wearing my hard hat.) Make sure they understand the reasons for all the safety rules. If the workers know why they have to wear goggles, they are more likely to wear them.