Guys... Don't even bother with these pieces of crap. I am a paintballer and I saw these grenades in action at several occasions. I can honestly say that 6 times out of 10 they do not work, no matter what kind of temperature. These are manufactured directly from Taiwan so it explains the lack of quality control.
Here's the direct link to the manufacturer's website:
Even as an experienced paintballer, I would not recommend this product to anyone (and especially not airsoft players LOL)