"I would like to think sparkler bombs are a thing of the past, but there are plenty of places on the internet where you can learn to create something like that. Sparkler bombs are exceptionally dangerous, not just to stand by, but also for the people putting them together."
Manipulating any fireworkscould bring a prosecution, Mr Bain added.
One of the more common but avoidable fireworks mishaps was using a lighter to read instructions on fireworks, Mr Bain added, and said a bucket of sand or water should always be kept on hand.
HazSubs runs approved handler courses for large fireworks displays and a spokesman said it was fortunate that the age of modifying fireworks was largely a thing of the past.
"When I show a picture of a sparkler bomb, I look around and see if people are nodding and smiling," HazSubs operations manager Aaron Donald said. "Half of the people don't recognise sparkler bombs any more."
However, Mr Donald said people will always need reminding.
"As part of my presentation I bring to people's attention the facts around sparkler bombs and the danger they pose. Changing the characteristics of a firework in any way is against the Hazardous Substances and New Organism (HSNO) Act. If you're altering a firework in any way, that is an offence. So when you get these kids putting a bunch of sparklers together, turning it into a bomb, while they run the risk of maiming, they're committing an offence."
Mr Donald was hesitant to describe tying sparklers together as a criminal offence. "You might be splitting hairs, but if you're changing the characteristic in anyway, if you cut the top off and pour contents into a coke bottle ... Clearly sparklers say on the packaging 'light only one sparkler at a time'. So if you strap them together, if that's resulted in damage, they could look at that as breaching the HSNO Act."
Fireworks are permitted to be on sale for four days prior to and including Guy Fawkes Day, from tomorrow until Wednesday. Restrictions imposed in 2007 means no more than 50 sparklers can be purchased mixed in with bulk packs. NZME