WHY FIT A FAN IN AN INCUBATOR?

Brinsea Products, the Incubation Specialists explain the difference between still air and forced draught

There are two distinctly different kinds of small incubator, those with a fan and those without a fan; ‘forced draught’ and ‘still air’ and users are sometimes confused by the choice. The difference in the way eggs are warmed is important but often not fully appreciated. Here are some of the considerations.

To achieve good lateral temperature consistency, ‘still air’ incubators (those without fans) are generally heated from above the level of the eggs and exhibit a marked temperature difference between the upper and lower levels, so that the tops of the eggs may typically be 4°C (7°F) warmer than the bottoms. Introducing a fan into the incubator dramatically changes the situation, eliminating temperature gradient for all practical purposes. Obviously, if eggs are to be set on different levels in the same machine it is essential to circulate the air mechanically so that all the eggs are exposed to the same temperature. However, since many of us are concerned with relatively small numbers of eggs which can all be set on one level there is a real choice to be made.

As well as eliminating the temperature gradient a fan also eliminates variations in the Relative Humidity. R.H. is closely related to temperature (see Brinsea information sheet ‘Humidity in Incubation’) in such a way that (for a given volume of air) the relative humidity reduces considerably as temperature rises. The following example of a still air incubator indicates the kind of variations which may be expected.