Do fire extinguishers need to be mounted inside the cab?

That is exactly where I mounted mine.

 

Here’s the actual regulation: 303.95(a) Fire extinguishers -

(1) Minimum ratings.

(i) A power unit that is used to transport hazardous materials in a quantity that requires placarding (See § 177.823 of this title) must be equipped with a fire extinguisher having an Underwriters' Laboratories rating of 10 B:C or more.

(ii) A power unit that is not used to transport hazardous materials must be equipped with either:

(A) A fire extinguisher having an Underwriters' Laboratories rating of 5 B:C or more; or

(B) Two fire extinguishers, each of which has an Underwriters' Laboratories rating of 4 B:C or more.

(2) Labeling and marking. Each fire extinguisher required by this section must be labeled or marked by the manufacturer with its Underwriters' Laboratories rating.

(3) Visual Indicators. The fire extinguisher must be designed, constructed, and maintained to permit visual determination of whether it is fully charged.

(4) Condition, location, and mounting. The fire extinguisher(s) must be filled and located so that it is readily accessible for use. The extinguisher(s) must be securely mounted to prevent sliding, rolling, or vertical movement relative to the motor vehicle.

(5) Extinguishing agents. The fire extinguisher must use an extinguishing agent that does not need protection from freezing. Extinguishing agents must comply with the toxicity provisions of the Environmental Protection Agency's Significant New Alternatives Policy (SNAP) regulations under 40 CFR Part 82, Subpart G.

Where does the regulation say the fire extinguisher must be inspected yearly?

Where does the regulation say it must be accessible without a key?

 

The regulation is “common sense “!
If you need a fire extinguisher you need it fast. Why fumble around for a key?

 

Depending on which make of tractor mine(Kenworth) is mounted (and secured) between the drivers seat and the door on the floor near the battery shutoff switch. Our Freightliners have theirs mounted and secured on the floor behind the passenger side seat.
Since my employer is hazmat rated we have 10 B.C. extinguishers.