During the entire shoot there was no actual pyrotechnics present or used on set. Every single explosive shown in the series was, in fact, a visual effect.
In Decker Season 2, episode 2, you will notice Gregg Turkington has a 'blink and you'll miss it' cameo as a bar patron while Decker is singing.
This makes Gregg Turkington the only actor to have played two separate roles in any season of Decker.
The third season, Decker vs. Dracula, is no longer considered in canon, as the series was not finished due to creative differences between star Tim Heidecker and director Gregg Turkington. The new series, Decker: Unclassified, is considered as the series to follow Decker: Port of Hawaii.
Decker is the sister production of On Cinema, another adult swim series starring and created by Tim Heidecker and Gregg Turkington. A number of jokes in the series are inter related between the two shows. Per example, in the show On Cinema Gregg plays himself as a nerdy film buff who collects a VHS tapes that he carefully catalogs with a code. In the second season of Decker, the eponymous character collects all of Greggs collection and burns them. This is commented on in On Cinema that Tim thought they were "fakes". In S5 EP2 of On Cinema Tim leads Gregg in a strange interview in front of a green screen, which is actually a ruse by Tim's character to get Gregg to fill lines for his show Decker in S1 EP3.