its not anything i would be even remotely concerned about.
just dont use shitfire chinese ied batteries.
its not a super demanding light anyway.
even laptop pulls are fine in it.
It’s not gonna explode.
Someone did an experiment with some light containing a cell melting down. The switch cover blew out with a plume of fire. This was somehow done on purpose. I seriously doubt there is any real danger if one uses nothing but good cells and the light has LVP or if not the cell has a protection circuit. No cheap cells.
Knowing that, if anyone is still concerned that their lithium cell flashlight may explode I believe they should use lights that use alkaline cells or maybe Eneloops.
Yes, if you are concerned about having an explosion, this is a great idea. To be a little more specific, drill the holes in the battery tube. Probably doesn’t matter where or the size, but maybe 1 on top and another on the bottom. If you are that worried about it, maybe just get some protected batteries.
Please remove battery first (even if the battery has protection). 
This is the video MtnDon refers to:
Related thread: FORCED-VENT 18650 in a Flashlight: >> first VIDEO is online!
I had a couple of in parallel Samsung 26Fs short out because of a pierced wrap with copper sheet, and nothing blew up. I just found the battery pack was unusually hot by its left side, and I knew something had gone wrong.
I really doubt there's any real risk with this stuff, cell energy density still is nowhere near dangerous in case of a dead short. Of course, others may think different, but honestly, take a look at that video & thread before drawing any meaningful conclusions.
Cheers 
Just beat me to it… :laughing:
LoL, These were my thoughts exactly. Except, I would have said PocketFire batteries.
Past flashlight community experience shows that the whole tail cap generally blows off with much damage to the surroundings and sometimes user. Those were almost all cases with multiple cells in series. IIRC, the vaping community has discovered that holes near the cell vents are much more effective than near the tail. This is a good question you are seeking a safety relief should the normal procedures of using healthy cells, etc fail.
If doing so offers you peace of mind then personally I would just drill a hole in the flat of the battery tube & then I like the suggestion of just filling it with a little of silicone. Aesthetically I think it would look okay. But I’m not super sure if a hole over there would bother my grasp of the light.
If I was worried about venting making sure all the fire and fumes blow away from me would be a priority. Is doing something with the lens o-rings possible?
The most likely cause of a good quality protected cell venting would be water in the light so it still needs to be sealed up pretty good.
There was a HJK high drain battery test on this forum fairly recently that I can’t find. During one of the high draw tests a fuse opened up inside the battery making it permanently dead. IIRC the purpose of the fuse was to kill the cell’s output before it vented and seemed like it was common practice among quality cells. Did anyone else read that post?
I did. Something like 30A, no?
I did a cell venting in a flashlight test. I could not get laptop cells to vent with power surges as high as 120 volts AC from a 3000 watt generator or a direct 12 volts DC from a 700CCA car battery.
The only way i could get them to vent in the light was heat the cell (flashlight body) with a remote propane torch.
here is the video: >> https://www.youtube.com/watch?v=6acpwEqp5zg&t=18s
Water would not cause a cell to vent…
I think you are waaaaaay to paranoid about lithium cells.
Test/review of Shockli IMR26650 5500mAh (Black) 2017
Maybe temperature triggered, although a bit low I believe. PLB's 5.5Ah NiCoMn cell, surpasses both capacity and discharge ratings at the same time. Take that big brothers! 
Right now, PLB is ripping all of the remaining 26650 li-ion players a new one.
Cheers ^:)
From my understanding on this, the gasses developed in a venting 18650 are created so rapidly that you’d need some huge holes to prevent pressure build-up within the light body. Many small holes might help or might not, this kind of gas production nears a low-velocity explosion and any kind of restriction will have a notable effect no matter how small that restriction is.
Having said that, the actual chances of you experiencing this kind of an issue are minuscule if you use good cells wisely. The real danger of LiIon venting is the hydrogen flouride in the vented gas itself- you must know when not to breathe as even a small amount of that stuff in your lungs can make the rest of your life permanently miserable. Large quantities will make your remaining miserable life short.
Cells will heat up before venting. If you have a light in your hand and it heats up suddenly you will likely notice and be able to toss it safely out of range or remove the cell before it vents and/or causes the body to explode. If you’re not holding it you still get the HF gasses and flames. So really, I can’t see where drilling a flashlight body for this reason would be of much use at all. Just my $0.02 and YMMV but remember that I have watched my C8 with an 18650 in it go boom in a car fire so I’m not just speculating here 
Phil
@sawmaster: I was thinking that to, that the light would heat up so hard you’d just throw it away. That’s why I didn’t understand all the accidents with vaporizers blowing up in peoples faces. But apparently the space between the battery and the body of the flashlight/vaporizer is enough to act as insulation so that the battery heats up significantly faster (and more) than the body of the FL/Vaporizer. This could be the reason that people still use their vaporizer and have it blown up in their face before they even realize somethings wrong with the battery.
Whilst not meaning to play it down to much - using/charging li-ion cells should always be treated with care and respect,especially if more than one in series - but to put it in perspective using a well respected torch like the s2 with a single quality 18650 cell that you know the history off, is probably up there with putting on a pair of trousers in terms of user safety/risk for especially someone who’s taken the time to join blf and enquire about safty 
So personally I’d take the normal precautions you would/should with something powered by li-ion and not worry about it to much
No one should underestimate the dangers of wearing jeans…
http://www.onuavafertility.com/skinny-jeans-a-fashion-fad-threatening-your-health/