[beezle]

per a calculator on unsaferguard.org 20g of RDX

Injury/Fatality to Personnel Range (m) Fatal Distance 0.64 Lung Damage 1.02 Eardrum Rupture 2.63

[Eduard]

So apparently, it must be less than 20 g of RDX, and/or a weaker explosive: if the fatal distance was within 0.64 meters, there would be significantly more reported deaths.