CO2 during brooding: warmth without stale air
Brooding closes the house to hold heat, and gas heaters add CO2 to it. How to keep chicks warm without letting CO2 build up, and what to measure.
Air quality 4 min read
Day one. The house has been heated for a day before placement, the chicks are spread under the brooders, and the temperature on the controller is exactly where the management guide says it should be. The house is closed tight, because every gap lets expensive heat out.
This is the stage when temperature is easiest to read and air quality is easiest to forget. It is also when carbon dioxide is most likely to build up, because everything that keeps the chicks warm also keeps the air in.
Where the CO2 comes from
Two sources matter in a brooding house.
The birds. Every bird breathes out CO2. Chicks are small, but there are many of them, and in a closed house their output accumulates.
The heaters. Direct-fired gas heaters and brooders burn inside the house and release their combustion gases into it, CO2 among them. That is efficient for heat, since nothing is lost up a flue, and it means the heating and the CO2 rise together. The colder the night, the harder the heaters run, and the more CO2 they add to a house that is already on minimum ventilation.
Indirect heaters that vent outside remove most of the second source. The first one, the birds, is always there.
Why the thermometer does not tell you
The climate controller’s main job during brooding is to hold the target temperature. The cheapest way to hold heat is to exchange as little air as possible, and a controller can do that very well: the temperature line stays flat and on target while the air behind it gets worse.
That is why temperature alone cannot tell you whether minimum ventilation is enough. Temperature says the heaters are keeping up. It says nothing about how much fresh air the chicks are getting. CO2 answers the second question directly, because it rises whenever air exchange falls behind what the birds and the heaters are producing.
What limit to work to
The limit that binds you is the one in your welfare standard, integrator contract or breed management guide. As a reference, EU Council Directive 2007/43/EC requires CO2 not to exceed 3000 ppm and ammonia not to exceed 20 ppm, both measured at the level of the chickens’ heads, for broilers kept at higher stocking densities.
For chicks, “the level of the chickens’ heads” is very close to the litter. A sensor mounted at the height you would use in the final week reads air that is not what the chicks are breathing on day three. Mount the sensing point low during brooding, in the area the chicks use, and away from the heaters’ direct exhaust.
Finding the balance
Brooding is a trade between heat and air. Too little ventilation and CO2 climbs; too much and the heating bill climbs, and the chicks get chilled. The point of measuring CO2 is to make that trade on evidence.
In practice:
- Watch CO2 at night. The coldest hours are when the heaters run hardest and ventilation is lowest.
- Raise minimum ventilation in small steps when CO2 regularly approaches your limit, and watch what the temperature and gas use do in response.
- Compare houses. If one house runs higher CO2 than the others with the same settings, check it for blocked inlets, a heater problem or a different stocking.
- Keep the history. The next flock starts with the settings that worked, instead of starting from the manual again.
Humidity and ammonia come next
A closed brooding house also holds moisture. Chicks, heaters burning gas and drinkers all add water to the air, and without enough exchange it stays in the litter. Wet litter early in the flock is what drives ammonia later, so a brooding period with high CO2 and high humidity often shows up later in the flock as an ammonia problem.
That is the reason to read CO2, humidity, temperature and ammonia together from day one. See safe ammonia levels in a poultry house for how the story continues.
Heater and fan failures
The same closed house that makes CO2 a concern also makes equipment failures urgent. If a heater fails on a cold night, the temperature drops quickly. If the fans that provide minimum ventilation stop, CO2 and humidity rise. An alert on temperature catches the first; a current sensor on each fan and a CO2 alert catch the second. See what happens when ventilation fails.
How Henlytics measures it
Henlytics puts a fixed CO2 detector in each house next to the ammonia, temperature and humidity sensors. The GF-201 CO2 detector reads 0-5000 ppm with 1 ppm resolution and a response time of 15 seconds or less (T90), shows the value on its own display, and has alarm relays for a local siren. Readings go by cellular to one dashboard for every house, with phone alerts at the limits you set, alongside the climate controller you already run.
See ammonia and CO2 monitoring for the sensors and how they are installed.