All depends on what you want to use it for, helmets like this are great for lightweight sport climbing etc, but the construction is similar to bicycle helmets to an extent. Great for protecting against short falls and small rocks etc and they are incredibly light weight, but if you take the brunt of a fall or big rock on it, could do you some damage still. The outer shell is not made from rigid plastic like traditional helmets so if you're using it in mines or anything like that, it wont last too long if you're prone to banging your head and shit. That said, they're incredibly comfortable to wear.
If you're looking for something for underground/drains/caving etc, you'd probably be a lot better off with the good old 'camp' helmets, they're a rigid build and great for just bumping around taking big rocks on. Something like the Mammut El Cap or the Black Diamond Half Dome would be up your street. They're designed for big wall climbing, so they light, comfy/nicely padded and have a rigid solid outer shell, making them ideal for this kind of thing. Go Outdoors stock both...
Mammut El Cap Climbing Helmet | GO Outdoors
Black Diamond Half Dome Helmet | GO Outdoors