Allowing the interior temperature to rise above freezing point risks weakening the shelter significantly, especially if the outside air temperature is near freezing. A small hole for air circulation should be poked through the ceiling. To avoid dripping melt-water, irregular or bumpy surfaces are often smoothed to direct the flow of water down the walls to gather around the edges. A non-airtight fabric door cover will minimize the amount of cold air coming into the quinzhee. An empty, well built snow structure, 16 or more hours old, in weather below may be strong enough to support a group of adults standing on top of it.