Hello. :)
I have worked on Joseph's scba unit today. Here is a better sketch with some color ideas. Because of the amount of gray and black, I wanted to make sure that it was all still visible and not too similar in contrast (that makes it hard to tell things apart, I think). An example is his air tube being a darker color than the straps (which is darker than the metal, etc.).
In hopes of making this realistic, I drew his pressure gauge (the thingy that measures how much air that he has) "upside down." This is so that the firefighter can read it from their perspective. It's similar to the military practice of wearing a watch inside the direction of the wrist as opposed to the outside or why emergency vehicles (ambulances, etc.) have their lettering backwards.

Also, I made him a custom logo for his scba. :) It's from the Hawaiian word ea meaning "air."
I hope to draw his mask soon.