This I found on the Internet somewhere. From a British reenactor writing about the use of pyrotechnics at events. (My comments in italics.) - Jonah

Even "safe" pyrotechnics can cause serious injury - over 28/29 August (Bank Holiday weekend here in Britain) there was a Sealed Knot event in Oxfordshire during which a cannon backfired somehow, setting alight a whole swathe of field behind it (very dry stubble), which then spread to the car park - sending quite a few cars up in flames. Over 40 people were hospitalized, 27 of these being kept in overnight. Sounds commendably authentic!

Yes..I must echo some concern for battlefield pyrotechnics. I participated in an English Civil War Society event last summer in Bradford and was frankly quite shocked by practices that would send American insurers running for the doors. Cannon crews loaded turf in their charges, in one case sending a magnificent wad of grass arcing over the field into the backplate of a Royalist cavalryman! Sounds like they were reenacting one of the dirt clod battles of my youth rather than the English Civil War... The gun crews fired as quickly as they could load, and with little consideration for the position of the foot and horse (who were often in front and to the side of a gun) the concussion was quite noticeable.

At a Sealed Knot event in Edinburgh, charges detonated on the field were "beefed up" by plastic bags of flammable liquid (gasoline?) that ignited piles of straw placed over them. Heh heh heh. Cool. The smoke and flashes were exciting, but it sure worried me. Wuss. Finally, I must ask why anyone would want to use pyrotechnics on the field; to get a more "authentic" appearance? If that is so (and it would be a bit disturbing if true), where is the carnage? Usually in the parking lot after everyone has had their fill of beer. Where do the spectators see the bloody effects of a round of grapeshot tearing through a company of men? Where are the sounds of maimed horses and men? Where are bits of bodies strewn over the field and faces of the participants? Calm down, already. The really "authentic" groups will splash catsup or theatrical blood on themselves and run around the field screaming - to which the crowd usually responds with laughter (disturbing) or applause if it is a soldier from the "bad guys" (really, really disturbing). Who do we think we are fooling? Only yourself, pal.

Which leads to my frequently repeated complaint that BATTLE REENACTMENTS do not resemble battles very much at all. That is probably good, since many people who experience real ones are not eager to experience them again, and most people who watch them are disgusted and wish they hadn't. Hmf. Be a pacifist, then. See if I care!