When you sprayed the canned compressed air into the shredder it was still enerized. Canned compressed air discharges from the can in liquid and turns to a gas very quickly. The liquid caused a small arc in the shredder. This ignited the propane propellant used to discharge the compressed air from the can. The propane is what caused the house to blow up in myth busters.:)
I registered here just to let you guys know that I just had a paper shredder explode. A Royal VF810 I had purchased at Sam's Club about 3 years ago. It gets occasional use by my Safety guy. Yesterday, he went to shred a piece of paper and the shredder was running but would not feed. He pushed the reverse button to clear the shredder and an explosion occurred. A ball of fire came out of the shredder, singing his face and hands.
We are both trained accident investigators. After reviewing what had happenned, it appears that paper dust was ignited from a spark from the AC motor. The explosion bulged the lower paper container, blowing a small clear plasitic piece off. The shredded mechanism itself appears intact. The underside of the shredder is slightly blackened and the paper remains in the shredder mechanism are charred slightly.
Nothing unusual was ever put in the shredder and it has received normal maintenance as specified in the owners manual to include regular cleaning and oiling, using shredder oil. It had been about 3 months since maintenance was done and the shredder hopper was emptied the day before.
As I write this, the shredder is in my office, waiting to hear if the company or the US Consumer Product Safety Commision wants to examine it.
Doing alittle internet research (I Googled "exploding paper shredder"), I found 4 other examples of Royal model VF1000 exploding, one which resulted in injuries to a child. Emails and phone calls to the company have gone unanswered, but the US CPSC is very interested in the report I filed.
not so sure about a paper shredder exploding, but MCAS Cherry Point's generals building burned down a few years back due to a paper shredder motor overheating and igniting the shredded paper in the bin over a holiday weekend inside a vault like room that was unable to be accessed... interested to see what the final cause of this will be...