An ITE circuit breaker with a single pole is used for a 120-volt circuit. A clock radio, console video game or answering machine can run on a 120-volt circuit with no problems as there are no heavy-duty motors, compressors or other high-draw devices which require more from your electrical system. An air conditioner, refrigerator or washing machine demands more. These devices must be run on a 220-volt circuit and for these appliances a dual-pole ITE circuit breaker (or other brand) is required.
The dual-pole circuit breaker allows these high demand appliances to operate safely. In the case of kitchens and laundry rooms, a dedicated circuit is required for items like the dish washing machine or clothes dryer. These requirements are spelled out in building codes for houses and apartment buildings; they are not optional. If you aren't sure what is required for your home, contact an electrician and get some expert advice before you make modifications to your home's electrical system.