OSHA 1910.136(a) states that:

General requirements. The employer shall ensure that each

affected employee uses protective footwear when working in

areas where there is a danger of foot injuries due to falling

or rolling objects, or objects piercing the sole, and where

such employee’s feet are exposed to electrical hazards.

And from 1910 Subpart I App B:

Some occupations (not a complete list) for which foot

protection should be routinely considered are: shipping and

receiving clerks, stock clerks, carpenters, electricians,

machinists, mechanics and repairers, plumbers and pipe

fitters, structural metal workers, assemblers, drywall

installers and lathers, packers, wrappers, craters, punch and

stamping press operators, sawyers, welders, laborers, freight

handlers, gardeners and grounds-keepers, timber cutting and

logging workers, stock handlers and warehouse laborers.

What this means to you is that if you perform any type of work where there is a danger of foot injuries, you need to use OSHA approved footwear. The old standard that OSHA used to define as acceptable was–ANSI Z41-1999, but in 2005 it was changed to–ASTM F2412-05. It appears that the only difference is the testing organization that wrote the standard. Now instead of seeing ANSI z41.1-1999 marked on a safety shoe, you’ll see ASTM F2413-05.

On protective footwear that isapproved, the first line of the marking will now be ASTM F2313-05.
The second line of the marking will also tell you a few things about the footwear. This line takes the form:

(M or F) I/(75 or 50) C(75 or 50) Mt/(75 or 50)

M or F = male or female

I/(75 or 50) = Impact resistance (75 or 50 foot pounds)

C/(75 or 50) = Compression resistance (2500 or 1750 psi)

Mt/(75 or 50) = Metatarsal Protection (75 or 50 foot pounds)

The third and fourth lines are for specific types of hazards that the shoe is rated for. These can be PR (Puncture Resistance), CS (Chainsaw Resistance), EH (Electrical Shock Hazards), DI (Dielectric Insulation), SD (static Dissipative), Cd (Conductive)

An example of a safety marking on an approved shoe is:
ASTM F2413-05
M I/75/C/75/Mt75
PR
EH

Check prices on Safety Shoes here!