Pull the context and count to three sentences
Let's imagine an army has created a kind of explosive similar to grenades, but much smaller in size while maintaining a good chunk of offensive output.
Known simply as "flakes", you can hold a good 8-12 in one hand, and due to their higher numbers, you can target a much wider area, such as big, open-field battles.
They work like a mix of incendiary, suppressing1 and concussion grenades, doing the most physical damage by the sheer explosive force, then ejecting a hot, incendiary liquid in its vicinity, potentially igniting covers and frightening even more anyone who heard and saw the explosions2.
My question is : How can I make these explosives safe for the grenadier?
So first, let's talk about harm capacity : Flakes are known to be really dangerous to anyone under a 1 meter (~3.3ft) in radius, combusting with a powerful invented chemical (either powder or liquid). But also remember there is a small incendiary left-over, which is prone to expand and force a tactical retreat to anyone standing near in the minute after the throw. We don't really want them exploding near us too much so, more at a good distance to have some time to adapt to the battlefield.
The technology to make it safer can go as high as today's technology. As far as I am aware, modern civil explosive devices use a remote detonator, like for instance professional firework shows and building destruction companies, but in the case of grenades it's more often controlled by chemical fuses triggered by a lever you pull3 : after you pull the lever, a small hammer is thrown full force towards a spark-inducing plate, igniting the fuse.
Disregarding the fuse reduced length due to the tiny size, the problem with modern timed grenade system is that, wellie... You'd need to pull the pins of every flake, which could be quite an hassle given you have 8 times more. Moreover, I want them to be thrown in groups, kind of like a shotgun shoot many pellets at once, and the above point prevent this. Therefore, and as you probably guessed it : how can I control when the grenade becomes dangerous is the main issue to me and the reason I ask here.
Since I've thought a little through the matter, I know you might also be interested in something which could be easily forgotten : How to ensure you don't lose a flake while throwing them. Indeed, when you have a big handful of tiny grenades in your bare hand, it's easy to slip one of them. I decided at the time of writing to put them inside a big shepherd sling, then spin it vertically in formation and horizontally when alone, and finally reload by just grabbing a bunch of flakes from a pouch. It's a little bit "rustic", yes, but I don't wish to use firearms for that matter, including grenade launchers. However, if there's a more appropriate way of sending the flakes with your ignition technic (excluding grenade launchers), you can consider it as an annex, bonus question. Still, remember this is only secondary and not the main topic here, and if you do decide to extend on this, that flakes must be delivered to the enemy in groups.
Final tusk of interest : these grenades are carried by explosive specialists, so expect them to carry quite a few of them in their backpacks. Also note that they work with other soldier units, so the solution of having them being heavily armoured and fireproof is nice, but not a solution for their friend next to them.
So how can you increase the average number of days since last accident from 0 to a lot higher and comforting level for the flake grenadiers?
1 : By "suppressing", I mean the noise, multiple impacts and such are capable to deter the opposing side's morale and frighten out anyone out of cover.
2 : They aren't fragmentation grenades, because, well the shrapnels are too light to have enough kinetic energy to make meaningful damage ^^.
3 : There are also impact type grenades, which explode... On impact, but I don't know exactly how they work (I guess there's a "spark machine" in them, but it's just a guess), so I'm a little bit left out on it.