Pros
Great coaching/mentoring. Strong emphasis on hiring from within for new positions. There is a weekly notice to employees for new job openings. Many people that I trained before I left have been promoted to new and interesting positions. They preach safety and actually promote a safety-over-productivity culture, unlike many similar companies. Any employee has the authority to stop a job if something unsafe is happening. I personally took cross training opportunities that boosted my career. Everyone is generally great to work with. I saw a few terrible employees get fired, which was a plus compared to working with slackers in high-pressure situations. If you work hard, make an effort to be likeable, and take the opportunities presented to you then you'll do great.
Cons
My hours were ridiculously long; I worked 70 hours per week on average. This job was a grind; I had to work at a fast pace all day and every minute counted. This job required a fairly high degree of technical proficiency, but also a large amount of brute strength and physical stamina. You'll be an expert at identifying hazardous characteristics of chemicals, but you'll also be expected to load 450 lb drums onto a truck 2 feet above the loading dock. Maybe that was just me because I was willing to do it. I spent two days per week on one contract where I'd be collecting chemicals on foot for 5-6 hours, walking several miles, then I'd have to sit down to catalog and handle the chemicals for the next day and a half. One con is that there are many hands involved behind the scenes on a given job. Someone that is bad at your job might write your paperwork and badly inconvenience you. Or you might be waiting for an approval from someone that just doesn't prioritize your job, and wait for weeks for them to do a task that you could have done yourself in 30 minutes. Sometimes I'd be called in to finish the last 5% of someone's job, only to find that they left me with 75% of the work to do and I'd be delayed for my other jobs.