The need for adequate ventilation is commonly recognized in chicken farming, but it is not always appreciated that incubators have as much need of a good ventilation system, if not more. Chicken embryos need a highly oxygenated environment (19.6% vol.) for proper development, and carbon dioxide and heat are produced. Excessive heat can cause early hatching and dehydration, which often contribute to the mortality rate, while cold can cause slow development. Irregular hatching times can reduce overall production. A reduction in capillary flow due to inadequate oxygenation can also lead to ascites.

Excessively high temperatures can severely harm chick quality and hatchability in less than half an hour. Since close control of temperature is often needed, ventilation cooling may not be enough. Evaporative cooling is often used to supplement other systems, and also helps to increase humidity.

Investing in a reliable hatchery ventilation system adds value to the farm in many ways:

• Helps to ensure timely hatching
• Prevents bacterial contamination
• Reduces the risk of ascites
• Promotes high chick quality and thus better-quality stock
• Increases profit margins

If many embryos die in the shell, it is possible that ventilation is poor. Ventilation is likely to be the reason for poor hatchability if the dead embryos do not show signs of dehydration, disease in the yolk or malpositioning, most of them reach the day 19, the incubator dampers are closed more than expected, and there are indications that the temperature is high enough or too high.

Ventilation System Requirements

In order to fulfil its role, the ventilation system should have adequate pressure, humidity, and temperature control as well as sufficient airflow. Air supply is as important as temperature and humidity control. The rate of air exchange required will depend on the number and density of eggs, their stage of development and the outside air temperature and humidity. In general, slight positive pressure in the hatchery indicates good air supply.

It is important to remember that more ventilation is needed as the eggs develop. The need for oxygen increases from the egg-setting stage. The eggs shells have respiratory pores for gas exchange. For most of the egg’s development, the embryo’s lungs are unable to provide enough oxygen and remove enough carbon dioxide. Instead, two other structures, the vitelline plexus and the allantois, are the main respiratory organs in two successive periods of egg development. The lungs gradually take over the function of the allantois near pipping time. It is at this time that the highest rate of air exchange is needed.

The system should maintain even air distribution and temperatures throughout the entire space. Care should be taken to prevent microclimates in buildings that are less effectively ventilated. An adequate ventilation system will remove excess heat and moisture (thereby reducing problems with condensation) and reduce the concentration of waste gases (such as ammonia and carbon dioxide), dust and microorganisms by dilution.

Efficiency

The cost-driven nature of the poultry industry makes energy efficiency another important concern. The location of ventilation equipment is critical to the performance of the entire system. In order to prevent areas of stagnant air and maintain the right airflow velocities, fans and inlets must be located in the right relative positions. The efficiency and air volume flow rates that the fans are capable of will depend on what venting and accessories are needed and what other obstructions to airflow may exist in the hatchery.

Design Guidelines

There are many different ventilation systems in use. Among the ventilation solutions that are commonly employed in the poultry industry, roof-mounted fans drawing air from inlets on the walls and “reverse flow” systems where the inlets are in the roof and the fans are wall-mounted are often encountered. Well-designed systems have a number of elements in common.

Air should be exhausted to the outside of the building, usually with a ducting system. Without adequate exhaust vents, air will merely be circulated in the building and not enough oxygen will reach the eggs. Special care must be taken with small or closed rooms. Exhaust air is sometimes naturally removed, but mechanical systems more reliably maintain even temperatures throughout the year.

It often happens that several incubators operate in a room and take in and exhaust air into the same room. Doors and windows are sometimes closed to maintain the humidity and temperature of the incubator. However, this can result in poor air exchange. It is better to install inlet vents and exhaust ducts in the room or to ensure there are enough openings. Commercial incubators typically have dampers that constantly open and close as the temperature rises and falls. Since eggs produce less heat during early development, the dampers tend to stay almost closed at this stage.

For single-stage incubators, the total inlet and exhaust opening sizes should be roughly the same.

Ventilation systems should be easy to clean. Poorly cleaned ventilation systems combined with cycles of dry and wet conditions (for example owing to chick take-off followed by hatcher washing) produce conditions suitable for the proliferation of the mould Aspergillus, which is known to increase mortality, especially at day sixteen. Similar problems exist with evaporative coolers that are switched on and off at different times and air conditioning system filters.