NB-and-especially-C Weapons in T2K

[Raellus]

In my PbP, the player party has come across three 155mm vee-ex gas shells. They just command detonated two of them about 500m upwind (a very slight breeze) of where they are currently conducting house-clearing ops and I'm wondering if any of ya'll know what the dispersal radius/danger area is for such a weapon. I'd Google it but I don't want to end up on some kind of gov. watch-list. So, I'm hoping someone out there already has and can help me answer this question.

Thanks.