These ladders come in a variety of sizes and duty ratings (the total combined weight of the user and equipment). Ladders referred to as Single Entry are for use by one person at a time while Double Entry indicates that the ladder will support it's duty rating on both sides at the same time.
Duty ratings are assigned by OSHA and ANSI. The individual ratings are as follows:
Type III ladders are rated for a maximum of 200 lbs.
Type II ladders are rated for a maximum of 225 lbs.
Type I ladders are rated for a maximum of 250 lbs.
Type IA ladders are rated for a maximum of 300 lbs.
Type IAA ladders are rated for a maximum of 375 lbs.
