In your standard 20th and 21st century "Hollywood" war films you'll often see soldiers headed off to combat (and while in combat) with hand grenades strapped to their chest. Is this an accurate depiction of the way in which a soldier might carry an item so explosive? One would think that the risk of the grenade going off due to strikes from bullets/shrapnel etc... would be quite high and that other places on the body, such as the back of a belt pack, would be a less dangerous spot to keep such and item.
Ex infantry Sgt for the Canadian army, small arms instructor, not a historian though. Here I'll only talk about the fragmentation grenade, as I think this is what you are asking for.
1- A grenade has a very low chance to detonate if you fire at it. Look at this picture. The way it works is that the striker hits the primer cap, wich ignites the fuse (time delay), then the detonator. The detonator is the "dangerous part". It ignites the explosive charge (beige) by pressure and heat. The explosive charge is really stable. You can fire threw it, ignite it, it will not blow. The only possibility to set the grenade would be to hit the detonator. It is possible but not the greatest threat in combat.
2-Having a grenade in the back pack really nullifies the point of having a grenade, since it would take too much time to grab and throw it. If you have grenades in your back pack, it's for transportation only (like having 2 ready, and 5 in the backpack).
3- This is a grenade pouch . It is worn on (near) the belt, perhaps on a strap, normally on the side of the body. Since you'll normally use more ammunition than grenades, the front of the body carries magazines and stuff like that, but it's not a rule.
One of the main advantage of the grenade pouch is that it protects the safety pin (the ring) from being extracted by branches and the like. Even though the pin needs an effort to be extracted (you can't really do it with your teeth as in the movies) that would be more of a threat than being fired at the grenade. At least, you won't lose your grenades while crawling and running.
4-The only time where you could see someone with a grenade "strapped on their chest" is in the final part of an attack, when one soldier is designated to throw a grenade. If the soldier chooses to do it, he'll hang the grenade by the lever in a strap on his chest. But this will only happen for a couple of minutes, as the grenade is not secured.
If you want a quote http://www.umass.edu/armyrotc/Training/grenades.pdf chapter 3 figure 3.1 for the carrying and the grenade pouch. Remember that what is in the training books and what people do in real life is often not the same.
Edits: grammar, English is my second language.
If you just Google a few pictures of soldiers in Vietnam you can see them with grenades strapped to their chest - maybe less recognizable because we're used to the classic F1 grenade, but many real Vietnam pics show soldiers with RG-42s. This picture of an American soldier shows 2 can-bottle like grenades (RG-42) on his chest. http://41.media.tumblr.com/tumblr_lsrhb3xFuF1r0che3o1_250.jpg But sometimes you also see them on the belt - or not at all.
It's worth noting that regardless of it's location, it's still at risk of being hit by bullets/shrapnel. When you think about it, is an exploding grenade any better attached to your belt than your chest... It's gonna kill you anyways http://36.media.tumblr.com/tumblr_luf1u1Mk7L1r0che3o1_250.jpg http://dogatemytank.tumblr.com/post/9761690120/stephen-h-warner-1970-1971-us-soldier-vietnam
