You can actually see the spark around 0:48. Those look like rolls of expanded polystyrene/polypropylene foam insulation, and if so, I would bet that this is igniting the off-gassing isobutane/pentane that was used as the blowing agent. They should have let them completely off gas somewhere with proper ventilation, but who has time for that?
There are currently 1 users browsing this thread. (0 members and 1 guests)