Safe ammonia levels in a poultry house

You walk into the house at seven in the morning and the ammonia catches in your throat for a few seconds. Then it fades, the birds look normal, and the day starts. By the time anyone thinks about it again, the fans have been running harder for two hours and the air is fine.

That morning moment is the only ammonia reading many farms ever take, and it is the least useful one. It measures the air at head height, after the night is over, through a nose that has already started to adapt. This guide covers what limit to work to, where the reading should come from, and why the hours nobody sees are the ones that count.

What limit to work to

There is no single number that applies to every farm. The limit that binds you is the one in your welfare standard, your integrator or buyer contract, or your breed management guide, and your veterinarian can tell you which one applies.

As a widely used reference, EU Council Directive 2007/43/EC requires ammonia not to exceed 20 ppm, and carbon dioxide not to exceed 3000 ppm, measured at the level of the chickens’ heads, for broilers kept at higher stocking densities. Many private standards and integrator contracts are written in the same terms: a concentration in ppm, at bird height.

Two things follow from that wording. The limit is a concentration, so it needs an instrument rather than a nose. And it is defined at bird height, so a reading taken anywhere else answers a different question.

Measure where the birds breathe

Ammonia is released from the litter. Close to the litter, where the birds spend their day, the concentration is at its highest. At standing height, and especially near an open door or an air inlet, fresh air dilutes it.

A good measuring point is:

• At bird height, over the litter, where the head of an average bird would be.
• Away from air inlets and the fan end, so the sensor reads house air rather than incoming or outgoing air.
• Inside the zone where birds sit, not in a corner they avoid.

In a long tunnel house, conditions change along the length of the building. One detector in the middle of the house tells you most of what you need; a second one toward the fan end shows how much the air has picked up by the time it leaves.

Why the night is the problem

During the day, with birds active and temperatures higher, the controller usually runs more ventilation and ammonia stays down. At night, and through cold spells, the controller holds the house on minimum ventilation to keep the heat in. Less air is exchanged, the litter keeps releasing ammonia, and the concentration climbs for hours.

This is the part a morning walk-through cannot see. The reading at seven tells you where the night ended, not how long the house spent above your limit or how high it went at three in the morning. A fixed sensor logging every few minutes shows the whole curve: when it started to rise, how long it stayed up, and whether the morning fan increase brought it down or only slowed it.

That curve is what lets you adjust minimum ventilation with some confidence. Without it, every change is a guess between heating cost and air quality.

Wet litter drives most of it

Ammonia production rises sharply when litter gets wet. The usual causes are well known to any farm manager: leaking or badly adjusted drinker lines, high humidity that the ventilation is not removing, condensation on cold walls, and loose droppings from digestive trouble.

This is why ammonia is best read alongside temperature and humidity. A pattern of humidity staying high for a day or two, followed by ammonia starting to climb, points at moisture. Ammonia that jumps without any change in humidity points somewhere else. The four readings on one chart turn an ammonia alarm into a diagnosis you can act on next time.

Why your nose is not enough

People adapt to the smell of ammonia quickly. A house that seemed strong on entry seems acceptable a few minutes later, even though nothing has changed. The day shift and the night shift can walk into the same house and honestly disagree about it.

A number on a screen settles that. It also gives you a record: if a buyer, an auditor or your own veterinarian asks how the house has been, you can show them the history instead of describing an impression.

Setting an alert that is useful

A fixed sensor is only half of the job. The other half is being told when a reading crosses a line, and being told in a way that gets a response.

• Set the alert below your limit, not at it, so the team has time to raise ventilation before the house breaches the standard.
• Use different limits for different stages if your operation needs them. Brooding, with a closed and heated house, often runs differently from the final weeks.
• Make sure the alert keeps asking. A single notification at night is easy to miss. An alert that repeats until someone on the farm acknowledges it is much harder to sleep through.
• Look at the trend every morning, even when nothing alarmed. A house that came close to the limit three nights in a row is telling you something before it breaches.

For the related question of carbon dioxide in a closed, heated house, see CO2 during brooding. If ammonia keeps rising while the controller shows ventilation running, the next thing to check is whether the fans are turning: see what happens when ventilation fails.

How Henlytics measures it

Henlytics puts a fixed ammonia detector at bird height in each house, alongside CO2, temperature and humidity sensors. The GF-201 ammonia detector reads 0-100 ppm with 0.1 ppm resolution, shows the value on its own display, and has two alarm relays for a local siren. Readings go to a cellular controller on the wall and from there to one dashboard for every house, with phone alerts at the limits you set. It runs alongside your existing climate controller and does not change how the house is run.

See ammonia and CO2 monitoring for the sensors and how they are installed.