Formaldehyde is one of the most effective and cheapest ways to disinfect (hatching) eggs. However, the method must be applied in a strict way, with utmost precautions for the health of workers, as it is reported to be carcinogenic.

Formaldehyde is especially effective as it is a gas, which can be applied without wetting the eggs. As it is a gas, it penetrates easily in the stacks of eggs and in the pores of the eggs. The effectivity is based on its capacity to oxidize proteins. This will kill bacteria, viruses and fungi, but forms a potential risk for all animal tissue, including tissues of embryos and tissues of humans.

To avoid damage of the embryo, the time of exposure is particularly important, as this will determine the penetration of the gas into the egg membranes and into the egg.

It is advisable to use formaldehyde on hatching eggs for not longer than 20 minutes. After 20 minutes of exposure, ventilation of the room should be started.

When eggs are stored on paper trays, cartons or bags, we have to realize that it will take much longer to ventilate the formaldehyde away from the eggs, so the exposure time will be lengthened. For that reason, fumigation of eggs stored on these manners, is not recommended. Eggs should be stored on plastic trays or setter trays for proper fumigation.

As penetration of formaldehyde will damage the embryo, there should be at least 12 hours in between two fumigations, but a period of 24 hours is advisable to be on the safe side. Fumigation for eggs can be repeated, but not more often than once-a-day.

Once the embryo has started to develop, it should not come in contact with formaldehyde for the first 4-5 days. That means that between 12 and 96 hours of incubation, contact of the embryo with formaldehyde must be absolutely prevented, to avoid early deaths.