There's a lot to be concerned about... Pretty easy to get a sunburn from them if you are not careful, and they can also do some damage to your eyes as well. I always use a pair of tinted safety goggles and wear sleeves when working with the exposure unit.
In the US, you can't have an 'open' fixture without using a 'protected' lamp. The lamp will have an inner glass shield to keep molten glass from escaping in the event of a non-passive failure. If a fixture has been modified to remove the safety glass, I'd be very careful about using it for two reasons...
1. The aforementioned explosion risk.
2. There is likely a much higher UV-B emission if the safety glass is missing, so you are risking higher exposure.
From what you describe, this may be designed for open use, in which case, you are probably safe from explosions, but you still have to be concerned about UV exposure.
I would make sure the exposure unit has a good shroud around it to keep most UV from not escaping the exposure area. Minimize the time near the lights. Use safety goggles. Everything should be good.
---Michael