This episode was Aaron Paul's submission in the Best Supporting Actor in a Drama Series in the 2012 Emmy Awards- his third nomination and second win.
It only takes a pin head sized amount of ricin to kill someone in 36 hours.
In this episode, Walter is shown making what might be a pipe bomb and testing a remote detonator. The scene begins with a panning shot showing several instant cold packs cut open on his kitchen counter. Instant cold packs often contain ammonium nitrate, suggesting Walter's explosive of choice to be ANFO (ammonium nitrate fuel oil). Alternatively, some instant cold packs use urea instead, which can also be used to manufacture explosives.
The arrangement of the black tiles on the hospital floor is a deliberate mimicry and homage to the logo of the series' title.