In the days when I used to use a carbide lamp I always carried one or two spare lamp bottoms containing a charge of carbide, each with an individual screw cap. When the carbide ran out in your lamp, you could simply switch over the base and re-light the lamp. So carrying even 2 spare lamp bottoms gave you about 9 hours of light, comparing favourably with the electric lights in use at the time.. The amount of spent carbide left in the lamp base was insufficient to cause any problems if you screwed the cap back on tightly. So, despite using a carbide lap for many years, I never dumped carbide in a cave but always took the spent carbide out with me to dispose of elsewhere.Isn't there a risk of spontaneous combustion from pressure build up of Acetylene in a sealed container? This could apply to carrying (almost) spent Calcium Carbide out of caves.
I have wondered which came first in blowing up glass bottles - a popular pastime from before my time, which I would never indulge in of course. Would the bottle explode from the build up of gas pressure alone, or plus combustion pressures? If in my youth I had tried this stunt I could report that the result was dramatic but that question was unanswered.