Forced Air vs Still Air Incubator

The difference in one sentence

A forced air incubator has a fan that moves warm air around every egg, so the temperature is the same everywhere inside. A still air incubator has no fan: warm air rises, so the top of the incubator is hotter than the bottom.

Temperature settings for each type

The still-air setting is higher because the air around the middle of the egg is cooler than where you measure. Never use the still-air setting in a machine with a fan: 38.9 °C in a forced air incubator will overheat the embryos. For humidity by species see our temperature and humidity guide.

Which is better?

Still air incubators are simple and cheap, and work for a few eggs in a single layer. They cannot hold eggs on several trays, because each level would sit at a different temperature. That is why every multi-tray and commercial incubator uses a fan. Forced air also recovers temperature faster after you open the door.

Fan tips for forced air incubators

• Listen for the fan every day. A silent fan means hot spots and a failed hatch.
• Keep dust and chick fluff off the fan blades; clean after every hatch.
• Do not block vents or the fan with trays or towels.
• If the fan stops, the heater usually keeps running, so check the temperature straight away.

See how an incubator works for the other parts.