Catching a chill is one cause of death among newborn puppies. A whelping box bedded with soft blankets is usually not enough, and many breeders recommend using space heaters and heat lamps in addition to keeping their puppies' whelping boxes in a warm room free from drafts. Keeping your newborn puppies warm is vital to keeping them alive when they're at their most vulnerable.
Purchase a heat lamp that meets your needs. Some dog breeders use heat lamps intended for livestock.
Set up the heat lamp at least five or six feet away from the box to protect the puppies, as heating lamps have been known to start fires. You also might want to consider using a mesh safety net in case the bulb breaks or explodes.
Hang the heat lamp over a corner so there's at least a small corner or a side of the box the puppies can move to if they begin to feel too hot. You want the heat lamp set up so that it keeps the puppies warm, but you don't want the entire whelping box directly heated, otherwise you risk overheating the puppies.
Hang a thermometer on the inside of the whelping box. You want the temperature inside the box to be at least 35 degrees Cor the first week, 29.4 degrees Cor the second week and 26.7 degrees Cor the third week. After that, keep the temperature between 21.1 and 26.6 degrees C.