Yes, ammonia hurts chickens. Even at concentrations you might not notice yourself, ammonia damages their eyes, destroys the protective lining of their respiratory tract, and reduces egg production. The key threshold is 25 ppm: above that level, chickens experience measurable health and productivity losses. Since most of the ammonia in a coop comes from decomposing droppings in the litter, this is largely a problem you can prevent.
How Ammonia Damages Chickens
When chickens breathe in ammonia, it dissolves into their moist respiratory tissues and becomes corrosive. The first structures hit are the tiny hair-like cilia lining the trachea and lungs. These cilia normally act as a sweep, pushing bacteria and debris back out before it can cause infection. At 50 ppm, the number of functioning cilia in a broiler’s trachea and lungs drops significantly, and inflammatory markers rise. At 100 ppm, the damage is severe: the trachea fills with mucus and the cilia strip away entirely.
Once those cilia are gone, bacteria waltz straight into the respiratory system with nothing to stop them. This is why chickens in high-ammonia environments are far more susceptible to respiratory infections, even from organisms that wouldn’t normally cause problems in a healthy bird.
Eye Damage and Visible Symptoms
Ammonia above 25 ppm commonly causes keratoconjunctivitis, an inflammation of the cornea and the membrane lining the eye. Affected birds huddle together, rub their eyes against their wings, keep their eyes shut, and show obvious sensitivity to light. If you notice your chickens squinting or clustering with closed eyes near the floor (where ammonia concentrations are highest), the air quality in your coop needs immediate attention.
Effects on Egg Production and Growth
You don’t need extreme ammonia levels to see a hit to productivity. In a controlled study comparing laying hens in clean air (5 ppm or less) to those at 20 ppm and 45 ppm, the results were stark. Hens at 20 ppm laid 5.3% fewer eggs. Hens at 45 ppm laid 12% fewer eggs. Both groups also ate less, with daily feed intake dropping by about 8 grams at 20 ppm and over 16 grams at 45 ppm.
Body weight suffered too. Over a 20-week period, hens exposed to 20 ppm lost about 30 grams of body weight compared to those breathing clean air, while hens at 45 ppm lost over 70 grams. Egg quality declined across the board as well, with shell thickness, shell strength, and internal egg quality all dropping as ammonia increased. For broilers, research from the USDA found roughly a half-pound reduction in body weight at 7 weeks of age when ammonia exposure went from 25 to 50 ppm.
Behavioral Warning Signs
Before you see clinical symptoms, you can often spot behavioral changes. Hens in ammonia-heavy air spend significantly less time foraging and take longer to start foraging when given the opportunity. They also forage in shorter, more interrupted bouts, suggesting discomfort and distraction. These are subtle shifts, but if your normally active flock seems lethargic or reluctant to scratch around inside the coop, ammonia could be a factor.
Can You Smell It Before It Hurts Them?
This is where things get tricky. Humans can detect ammonia by smell starting at roughly 5 ppm, but sensitivity varies widely. Some people don’t notice the odor until concentrations reach 25 to 50 ppm, which is already at or above the harm threshold for chickens. So a simple rule: if you can smell ammonia when you walk into your coop, the concentration is already high enough to be a problem. And if you can’t smell it, that doesn’t guarantee your birds are safe.
Inexpensive ammonia test strips or handheld monitors designed for poultry houses can give you a more reliable reading. These are especially useful in winter, when coops are often sealed up to retain heat and ventilation drops.
Keeping Ammonia Below 25 ppm
Ammonia in the coop comes almost entirely from the breakdown of uric acid in chicken droppings. Moisture and warmth accelerate this process, so litter management is the single most important lever you have.
Ventilation
Good airflow is the fastest way to reduce ammonia buildup. Even in cold weather, your coop needs some air exchange. A well-placed vent near the roofline lets warm, ammonia-laden air escape without creating a draft on the birds. Many backyard coop problems trace back to winter ventilation being sealed off completely.
Litter Moisture
Wet litter produces dramatically more ammonia than dry litter. Leaking waterers, poor drainage, and condensation are common culprits. Keeping litter dry and friable (crumbly to the touch, not clumped or caked) goes a long way. If you can squeeze a handful of litter and moisture comes out, it’s too wet.
Litter Amendments
If ventilation and moisture control aren’t enough, chemical amendments mixed into the litter can neutralize ammonia at the source. Sulfur-based amendments are the most effective by a wide margin: applied at just 2% of litter weight, sulfur reduced ammonia emissions by 91% in controlled tests, and at 4% it eliminated virtually all ammonia. Biochar is a moderate option, cutting ammonia by 41 to 46% at higher application rates. Zeolite (a natural mineral) offers a more modest 20 to 33% reduction depending on the amount used. These products work by either lowering the pH of the litter or trapping ammonia before it becomes airborne.
Regular Cleanouts
No amendment replaces the basics. Removing caked or saturated litter, cleaning under roosts where droppings concentrate, and refreshing bedding on a regular schedule keeps the ammonia-producing material from accumulating in the first place. In smaller backyard coops with limited airflow, frequent cleanouts matter even more than in large, ventilated commercial houses.