Ammonia and CO2 in Poultry Houses: Safe Levels and How to Monitor Them

Most poultry houses still manage ammonia by smell. Someone walks in, decides it's a bit strong, and turns up the fans.

The problem is that human noses acclimatise fast, and people vary enormously in what they can detect below 50 ppm. By the time a house smells bad to someone who works in it daily, birds have been sitting in conditions that cost feed conversion for days.

This guide covers the ammonia and CO2 levels that matter, why they matter for different reasons, and how to monitor both without turning it into a full-time job.

Ammonia: two sets of numbers, two different concerns

Ammonia thresholds get quoted loosely because there are two separate standards in circulation and they aren't measuring the same thing.

The important line is the first one. Birds are affected well below the level that concerns human safety, regulators. Research consistently shows performance and health effects above 25 ppm, and welfare guidance for laying and broiler flocks generally targets under 10 ppm at bird level.

That matters commercially. A house sitting at 30 ppm is legally fine for the people walking through it and quietly expensive in feed conversion and mortality.

Above 50 ppm the picture worsens sharply. Respiratory tract inflammation makes birds more susceptible to viral and bacterial infection, and the spread of diseases like Newcastle accelerates. Above 100 ppm, you're into immediate risk.

One thing this guide is not about. Continuous environmental sensors track trends and drive ventilation decisions. They are not personal gas detectors, and they should not be relied on as worker safety equipment. If you need OSHA compliance monitoring for people, that's a separate class of certified instrument.

CO2: the gas that tells you about ventilation

Ammonia tells you about litter. CO2 tells you about air exchange.

University of Georgia research points to keeping CO2 below 5,000 ppm, with an ideal target under 3,500 ppm. The EU poultry standard is stricter at under 2,500 ppm.

Elevated CO2 suppresses immune response and reduces oxygen availability, which shows up as slower growth long before anything looks obviously wrong. But its real diagnostic value is as a direct proxy for ventilation rate. Rising CO2 with a stable flock means air exchange has dropped, usually because someone reduced minimum ventilation to save fuel.

That makes CO2 the more responsive of the two gases. Ammonia builds over days as litter conditions change. CO2 moves within an hour of a fan setting change, which makes it the better real-time feedback signal for ventilation control.

Where ammonia actually comes from

Ammonia is produced when microbes break down uric acid in litter. Four things drive the rate.

Litter moisture is the dominant factor. Dry litter produces very little ammonia. Wet litter produces a great deal. Most ammonia problems are drinker line problems, condensation problems or ventilation problems wearing an ammonia costume.

Litter pH matters because ammonia volatilises readily in alkaline conditions and stays bound in acidic ones. This is the mechanism behind litter amendments.

Temperature speeds microbial activity. Warmer litter produces more ammonia from the same material.

Stocking density and flock age raise the total load simply through volume of manure.

The practical consequence: if you're logging house humidity alongside ammonia, you'll usually see humidity climb before ammonia does. That gives you a lead indicator and a chance to correct ventilation before the gas builds.

Sensor placement: bird level, not ceiling level

This is where most monitoring installations go wrong, and the error is systematic rather than random.

Ammonia is lighter than air, so it rises. Mount a sensor at ceiling height and you will read higher than the birds experience. Mount it in the fan discharge and you'll read the mixed average of the whole house, which is lower than the worst areas.

Measure where the birds are. Roughly 15 to 30cm above litter level, which is where their heads sit.

Cover more than one zone. Ammonia is never uniform. The worst readings turn up near drinker lines, in corners with poor air movement, and at the end of the house furthest from the inlets. One central sensor describes the middle of the house and nothing else.

Keep sensors out of direct water spray from drinkers and fogging systems, and away from the immediate discharge of an inlet where incoming fresh air will give an artificially clean reading.

Log CO2 higher up, at bird level or slightly above, but placement is far less critical for CO2 because it mixes more evenly.

Log temperature and humidity alongside

Gas readings on their own tell you there's a problem. Environmental data tells you why.

A house running at 28 ppm ammonia with 75% relative humidity has a litter moisture problem. The same 28 ppm at 50% humidity with high CO2 is a ventilation problem. Same gas reading, completely different fix, and you can only tell them apart with the other numbers.

This is the argument for putting gas and environmental monitoring on the same platform rather than running gas detection as an isolated alarm. One timeline showing temperature, humidity, ammonia and CO2 together turns a reading into a diagnosis.

An air temperature and humidity probe rated across the full 0-100% RH range handles the environmental side. Poultry houses sit at humidity levels that defeat consumer sensors, so the probe needs to be specified for it.

Winter is when this gets expensive

Every ammonia problem is worse in cold weather, for a simple economic reason.

Minimum ventilation in winter is a direct trade between fuel cost and air quality. Turn the fans down and heating costs fall while ammonia and CO2 climb. Turn them up and air quality improves while the propane bill rises.

Managed by smell, this trade gets made badly in both directions. Some houses run too tight and pay in performance. Others over-ventilate and pay in fuel.

Continuous ammonia and CO2 data turns it into an actual calculation. You can run minimum ventilation as low as the numbers allow, back it off when the gases stay flat, and increase it the moment they climb. Most operations find the payback is in fuel savings rather than bird performance, which is not what they expected going in.

Stop managing air quality by nose

Ammonia and CO2 are two of the few variables in a poultry house where continuous data changes decisions immediately. You either ventilate more and pay for fuel, or ventilate less and pay in performance, and you can't optimise that trade with a walkthrough.

Browse external sensors for ammonia, CO2 and humidity monitoring on one platform, or start from a matched setup in bundles if you'd rather not spec the logger separately.

Running multiple houses and not sure how many sensors each needs? Tell us your house dimensions and ventilation setup at UbiBot USA and we'll help you place them. Getting the positions right matters more than the number of sensors you buy.

Frequently asked questions

What is a safe ammonia level in a poultry house? 

Below 10 ppm at bird level is the welfare target, with 20 to 25 ppm treated as a practical upper limit. Bird performance and health effects are documented above 25 ppm, well below the levels that concern human safety standards.

Can I just smell when ammonia is too high? 

No. People acclimatise to ammonia within minutes, and detection ability below 50 ppm varies widely between individuals. By the time a house smells strong to regular staff, levels are usually well past the point where they're costing money.

What CO2 level is too high for poultry? 

Research points to keeping CO2 under 5,000 ppm with an ideal below 3,500 ppm, and the EU standard is tighter at under 2,500 ppm. Rising CO2 with a stable flock almost always means ventilation has been reduced.

Where should ammonia sensors be placed? 

At bird level, roughly 15 to 30cm above the litter, in more than one zone. Ammonia rises, so ceiling-mounted sensors read high, and single central sensors miss the problem areas near drinker lines and dead corners.

Why does ammonia rise when nothing else has changed? 

Usually litter moisture. A leaking drinker line, condensation on a cold floor or reduced air exchange will all raise litter moisture, and ammonia production follows within a day or two. Logging humidity alongside gives you the warning first.

Do gas sensors for poultry houses work as worker safety monitors? 

No. Continuous environmental sensors are built for trend monitoring and ventilation control. Personal protection against hazardous gas exposure requires certified detection equipment, which is a separate product class.