I just put mine up yesterday.
I was going to get the Kiddie extinguishers at Lowes then found the local Fire extinguisher store that does the annual checks etc. and bought much better ones there for about $10 more each. I got Sentry ABC 10 lb fire extinguishers
I asked him what the regs were for a commercial shop since I like to be safe. I was told that the top of the extinguisher is usually around 32" to 36" from the floor, and that 5' is the may height the handle can be, and that the base must be at least 4" above the floor to keep the tank from rusting out.
He told me to put them near the doors and at that an extinguisher must be within 75' from any point in the shop. Im fuzzy on the 75' since my shop isn't that big.
He also gave me Fire extinguisher signs with arrows that are to be put on the walls high up on the walls(no specific height given). I put mine about 10' up.
I did put an extinguisher in the back of my shop so I at least have a chance to work my way out if I am trapped in the shop by a fire. I also plan to get an ax to go through the wall if I have to.
He offered to give me a copy of the codes but I declined, the info above was sufficient for me.
Hope this helps.
Chris