In the cold season, a poultry house must both stay warm and receive fresh air. Exhaust fans remove humid, polluted air, but where the cold outside air enters the house, at what speed and in which direction, depends on the inlet windows. A good, correctly adjusted inlet sends cold air to the underside of the roof so that it mixes with warm air before reaching the birds. An unsuitable or badly adjusted inlet drops that same air directly onto the chicks and the litter.
This article explains what an inlet window does, how its dimensions and installation height are determined, how it is adjusted and tested, and what to look for when buying. Technical figures are quoted from the Ross Broiler Management Handbook (2025) and the Cobb guide.
An inlet window (air inlet vent) is a frame installed on the side wall of the house with a hinged door or flap. In most houses, inlets are connected by cable or rod to a winch, and the control system adjusts their opening and closing. The Ross handbook considers this the most common minimum ventilation layout: a large number of side inlets distributed evenly along both walls of the house.
The main use of the inlet is in minimum ventilation, that is, when the house temperature is at or below the birds’ desired temperature and the aim is only to supply fresh air and remove moisture and gases such as carbon dioxide and ammonia. According to the Ross handbook, minimum ventilation operates when the house temperature is equal to or below the set temperature, or up to 2 °C above it, depending on bird age.
An inlet does not move air by itself. When the exhaust fans switch on, the pressure inside the house falls slightly below the outside pressure (negative pressure) and air enters at speed through the inlet opening. According to the Ross handbook, warm air collects at the highest point of the house. If the incoming cold air travels along the roof, it stays away from the birds, mixes with the warm air and, as it warms, its relative humidity falls and it absorbs more moisture from the litter. The result is drier litter and lower heating costs.
If the pressure difference is insufficient, according to the same handbook, air enters slowly, drops to the floor too soon, stresses the birds and may wet the litter. For this reason, inlets should always be considered together with the exhaust fans and the control system. To calculate exhaust fan capacity, read the article Calculating house ventilation capacity.
In the Iranian market, the most common wall inlet size is 30 × 60 cm, and larger inlets are used for wide or long houses. The table below shows the sizes and materials of inlets presented in the poultry inlet category of the Toyooran Sanat Pouya website:
| Model | Dimensions | Body material | Stated feature |
|---|---|---|---|
| 30×60 polymer inlet | Outer 30×60, inner 26×56 cm | HIPS polymer | Return spring, curved vanes |
| 30×60 inlet vent | 30×60 cm | UV- and impact-resistant HIPS polystyrene | Double-walled flap with compressed foam |
| 30×60 double-walled foam-filled inlet vent | 30×60 cm | HIPS polystyrene | Double-walled foam-filled flap, concealed spring |
| Pars inlet window | 30×60 cm | HIPS engineering polymer | Channel flap, stepped sealing edges |
| 35×90 large inlet | 35×90 cm | — | Graduated adjustable deflector |
| 105×30 large inlet | 30×105 cm | ABS | Aerodynamic door design |
| Inlet wind hood (light trap) | 56×31×23 cm, for 30×60 inlets | Anti-UV polymer | Mounted on the outside wall |
Inlet dimensions alone do not determine how many inlets a house needs. According to the Ross handbook, the total number of side inlets is determined by the house’s minimum ventilation requirement. The Cobb guide also states that inlet capacity must match exhaust fan capacity, and that the correct pressure is achieved by matching inlet area to fan capacity. In other words, ventilation capacity is calculated first, and then the number and size of inlets.
A common question is how high above the house floor an inlet should be installed. Technical sources do not give the height from the floor; they measure it from the roof and the eave, because the aim is for air to reach the underside of the roof directly. According to the Cobb guide, inlets should be installed as close to the roof as possible, about 30 cm below the eave (the top of the side wall). The height from the floor therefore depends on the side wall height of the house concerned.
Other points about the installation location:
The Ross handbook sets three conditions for inlets to work correctly:
The Cobb guide gives a rule of thumb for choosing the pressure: about 2.5 pascals of pressure drop is required for every 61 cm the air must travel. The Cobb guide’s table for houses with inlets on both sides:
| House width | Pressure | Air speed at the inlet | Air travel distance |
|---|---|---|---|
| 10 m | 20 Pa | 5.7 m/s | 5 m |
| 12 m | 25 Pa | 6.5 m/s | 6 m |
| 15 m | 31 Pa | 7.2 m/s | 7.5 m |
| 18 m | 37 Pa | 7.8 m/s | 9 m |
According to the same guide, if inlets are on only one side of the house and the exhaust fans are on the opposite wall, pressure and speed must be higher. Cobb also recommends that inlets be controlled according to the house’s static pressure, not by percentage opening or temperature, and that they be fully closed and sealed when the exhaust fans are off.
An inlet only works in a house without unwanted gaps. According to the Ross handbook, to test airtightness all doors and inlets are closed and one 122 or 127 cm exhaust fan or two 91 cm exhaust fans are switched on. The pressure inside should not be less than 37.5 pascals (for a house of about 1,850 square metres). The Cobb guide considers a pressure below 25 pascals a sign of poor airtightness. Leaks are usually at the roof ridge, beside exhaust fans, around doors and at the base of walls.
To see the air path, Ross suggests a smoke or streamer test: light streamers about 15 cm long are hung from the roof 1 m from the inlet and then every 1 to 1.5 m. The streamer near the inlet should press firmly against the roof, and the streamer in the middle of the house should move only slightly. At bird level, air speed should not exceed 0.15 m/s, especially for young chicks.
The Ross handbook lists the features of a suitable minimum ventilation inlet as follows, and the Cobb guide adds the last point:
In addition, the body material must withstand moisture, ammonia and cleaning agents, and the inlet size must suit the wall, the number and capacity of exhaust fans and the existing winch.
The price of an inlet window is not fixed and depends on these factors: size (30×60 or large models), body and flap material (HIPS, ABS, double-walled foam-filled flap), whether an adjustable deflector and spring are included, the need for an external wind hood or light trap, the number required, and whether the winch, cable or rod and installation are included in the order. For an up-to-date price, request a quotation.
An inlet admits fresh outside air into the house at a controlled speed and direction. In minimum ventilation, negative pressure directs the air to the underside of the roof so that it mixes with warm air and does not reach the birds directly while still cold. This helps keep the litter dry and reduces heating costs (Ross).
The Cobb guide sets the height from the roof, not from the floor: as close to the roof as possible and about 30 cm below the eave. The height from the floor depends on the side wall height of the house.
According to the Ross handbook, minimum ventilation inlets open at least 3 to 5 cm, and all open inlets should be open by the same amount. If the pressure is not sufficient at this opening, reduce the number of open inlets rather than opening them further.
The number of inlets is derived from the minimum ventilation capacity and the exhaust fan capacity (Ross and Cobb) and depends on the house dimensions, production capacity and inlet type. Given the house dimensions, a specialist can recommend the number and layout.
To choose the right inlet size and number, send the following: the length, width and side wall height of the house, the type of production and capacity, and the number and size of existing exhaust fans. A Toyooran Sanat Pouya specialist will recommend the inlet model, number and layout. If the house is being fitted out from scratch, see also the poultry house fit-out and renovation process and the ventilation and heating equipment.
Send the house dimensions and exhaust fan specifications.
Category: Engineering technical guide
Tags: Poultry inlet window, What is a poultry inlet, Inlet window dimensions, Inlet installation height, Poultry house minimum ventilation
Published: 2026-10-12