The answer is simply that by heating up the area in which bed bugs are found to 120 - 140 degrees for at least 4 hours kills most bed bugs and their eggs. However, reputable bed bug exterminators that use heat will routinely keep the home heated at that temperature for longer than the 4 hours.
The easiest way to achieve the high temperatures needed to kill the fleas and all eggs is to place your clothing, bedding and any soft furnishings you can into a high-temperature cycle on your washing machine. Followed immediately in the tumble dryer on the hottest setting for at least 30 minutes.
They heat up the place up to around 130, 140 F(60C) for a period of about 8 hours. The bugs can not live in that temp range so it kills them.
Bed bug heaters can save you from doing all of that without calling an exterminator. Seriously. Instead of tossing out all of your books, clothes, and electronics you'd just throw them in in the Zappbug Heater above, turn it on, and walk away. It can heat up to 120 degrees, which is the needed temperature to kill bed bugs eggs, nymphs and adults.
Black plastic bags in the sun might work to kill bed bugs in luggage or small items, if the contents become hot enough. Bed bugs die when their body temperatures reaches 45°C (113°F). To kill bed bugs with heat, the room or container must be even hotter to ensure sustained heat reaches the bugs no matter where they are hiding. 8.
How long does it take to kill bed bugs, at all stages, with heat? From the University of Florida, slide #11 of the PowerPoint below: 100 minutes at 106F 25 minutes at 109F 4 minutes at 113F 2 minutes at 117F 1 minute at 120F. Remember that this is the temperature you need to get the bug (or egg) up to for the requisite time.