Carbon dioxide

Carbon dioxide

In a sealed, airtight incubator, the CO2 concentration in the air can rise to 5,000-6,000 ppm in just a few days because the eggs release CO2 to the surrounding environment. This also changes the pH of the albumen. Many hatchery managers see this as a positive effect, as a high CO2 concentration at the start of the incubation process triggers the embryos to produce more blood vessels. In fact, some hatchery managers inject CO2 to stimulate this effect. You can utilise the embryos’ ability to cope with high concentrations of CO2 by keeping the air inlets closed and applying a non-linear weight loss pattern. But, be aware that the eggs will lose less moisture during the first few days. This lower moisture loss has to be compensated for later in the incubation process. This will mean increasing the ventilating level later in the process. However, this is in line with the needs of the embryos in the second phase of the incubation process (high heat production). This strategy is not always risk-free, because additional (higher) ventilation can mean some of the eggs are incubated too cold. For this reason, it is very important to treat the incoming air. As a compromise, the air inlets are often opened after 3-4 days, which reduces the RH of the air. This also reduces the CO2 concentration so that less correction is necessary at the end of the incubation process. Fresh eggs have a higher CO2 content in the egg white, so the CO2 in the incubator also increases quickly. With older eggs, part of the CO2 has already disappeared during storage, so the CO2 in the sealed incubator increases more slowly. The incubator has to be sealed airtight and kept that way, otherwise you will be unable to reach these high CO2 concentrations.

Setting to a maximum CO2 level

Ventilation in the incubator is often set to prevent the CO2 concentration from exceeding 4,000 ppm. The purpose of ventilating is to maintain this maximum CO2 concentration. Depending on fertilisation and heat production (time, breed, egg size, eggshell quality, etc.) you can calculate the ventilation volume in m3/hour. To calculate this, you need to know the properties of the incoming air. These properties - especially the air temperature and RH - should not fluctuate too much. If there are large differences between the temperature and humidity of the outside air during the day and at night, it is very complicated to accurately set the required volume of ventilation air. When the incoming air has a temperature of 25-27°C and values of 300-500 ppm CO2 and 50-55% RH, the incubator can easily maintain the optimal climate conditions for the eggs. Incubation time (days)CO 2 concentration in incubator (ppm) eggs stored for a long time (> 10 days) fresh eggs 1,000 2,000 3,000 4,000 5,000 6,000 10 2 3 4 Increasing CO2 concentration and storage time 0 copyright protected 5

CO2 concentration

In the air cell, the air is saturated with moisture and the CO2 increases. The CO2 concentration is always higher here than in the air in the incubator or directly surrounding the eggs. Broiler embryos can cope with 1.4% CO2 (14,000 ppm) in the first 10 days. It is therefore more important to use ventilation to control the relative humidity of the air rather than the CO2 concentration during the first few days. The focus of ventilation in the first days is therefore on removing moisture. In the first four days, an RH higher than 65% is not unusual if you keep the doors closed. When the CO2 concentration in the second part of the incubation process exceeds the desired value, ventilation is used to regulate the CO2.