Steel Toe shoes are rated by the American Society of Testing Materials (ASTM). Inside the shoe (back of the tongue) there should be a label that looks like this:
As per this article below is the meaning of each line.
"ASTM F2413-18 – The first line shows the specific standard that the OSHA approved footwear meets. As indicated earlier, OSHA shoes follow the ASTM standards. Every label, will, therefore, bear the ASTM mark followed by the particular standard used. The last two digits after the hyphen (18) indicate the year that the standard was updated.
M /1/ C– the second line specifies the gender of the user (M to mean men and F female) this is followed by the ratings for impact and compression resistance. In the sample used here, the safety shoe is meant for men and comes with the ability to resist impact as well as compressional force.
Mt EH– the third line contains any other specification that the OSHA approved shoe provides, such as puncture resistance, shock resistance, and so on. In our case, the shoe comes with the ability to protect the wearer against electrical hazards (EH) as well as offer metatarsal protection (Mt). This line will also contain Mt sign and the specific rating."
Especially important in a situation where an AED may be needed is the EH rating or Electrical Hazard Resistance. Workers Land explains, "Basically, if you’re working with electrical circuits, these boots can withstand 14,000 volts at 60 hertz for 60 seconds, in dry conditions, provided there’s no current flow or leakage above 3 milliamperes."
Another important consideration is "that the ANSI and ASTM standards only refer to the toe protection, soles and metatarsal guards that are built-in the boot by the manufacturer. Basically, neither regulation allows add-ons like strap-on toe and metatarsal guards."