Military or professionally used explosives generally have an insensitive main explosive charge. It can be various types of explosive compound, but the theme is that the main charge is not set off by kinetic shock or heat alone.

To set off most types of these explosives requires a detonator. This can take the form of a blasting cap or something inside of a fuze that acts similarly. These are filled with small amounts of more sensitive explosive materials. When the detonator explodes it creates simultaneous heat and shock that when it is contact with a main charge causes the main charge to explode. Detonators are detonated either electrically, through an electric match type spark; or non-electrically which can be from sources like a percussion cap, shocktube, burning time fuse, or detonation cord.

For particularly insensitive main charges there is sometimes an intermediate charge made of a more sensitive than main HE surrounding the detonator to ensure the main charge goes off. This is something that has also seen in insurgent IEDs, where the builders stretch out their supply of military main explosives by using them as intermediate charges for the homemade main charge.

The dangers of something like a grenade primarily come from the fragmentation that is propelled from the force of the explosion. The raw explosive pressure is dangerous at a very close distance, but the fragmentation is what is going to spread out and put holes in people. I wouldn’t trust any helmet to fully stop the pressure and fragmentation of any given HE grenade. I’m sure you could theorycraft up a grenade and helmet combination to make this work, but in practical application it’s not something you plan to do and live.

As for “picking up or kicking a pipebomb” homemade explosive devices aren’t built following a uniform safety manual. You have no idea what it’s filled with or how it was made. Some lunatic/moron might have filled their pipebomb with a mercury fulminate or TATP main charge that goes off at a wrong touch. Or maybe it’s filled with an aluminum-ammonium nitrite mix with a stripped lightbulb stuck in as the blasting cap and there’s almost no chance it goes off. Or it’s a more conventional black powder main charge with an obvious external timer but when you pick it up the hidden tilt switch inside completes the circuit to the detonator.

Which is all to say, no don’t just pick up and toss pipe bombs that you find on the street because there are so many variables to learn that no amount of “internet research” is going to make it a good idea.

Ocean mine.

Many sea mines of that era are actually activated by disturbances in magnetism! They’re pretty good about not going off unless something large and metal rolls up, since that’s their purpose, although anything really old is suspect of not working as designed. That’s why when somebody digs up (or just kind of has) an old bomb they detonate it on site instead of trying to move it.

WWII also saw acoustic mines used. Contact mines were and are around too, and I would guess if you don’t crush a trigger the same answer about only going off when conditions are met applies.

Modern low-sensitivity explosives can survive an actual plane crash without going off, and will burn instead.

helmet (why not just move the whole sentence into the text, OP?)

SSTF covered everything from here on pretty much perfectly.

On the off chance your helmet does successfully take that kind of punishment, and the blast wave is absorbed enough to not hurt the soldier, there still will be a bunch of hot gases escaping in every direction which isn’t great. Better than no helmet, though - the trick is just noticing the grenade, stopping, removing your helmet and gently placing it over top before it blows up, which is why that move isn’t actually a thing.

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