Swine Barn Air Quality Monitoring and Improvement

By Dr. Zubair Khalid, DVM, MS, PhD · 2026-08-14

Key Takeaways

Continuous ammonia exposure above 10-15 ppm significantly impairs pig respiratory health and performance by irritating mucous membranes and reducing ciliary function, predisposing to infections like Mycoplasma hyopneumoniae and PRRSV.
Inadequate ventilation, indicated by carbon dioxide levels exceeding 3000 ppm, allows accumulation of harmful gases and pathogens, necessitating increased air exchange rates adjusted seasonally and by pig age/weight.
Dust, a complex mixture including feed particles and dried manure, carries bacteria, viruses, and endotoxins that cause lung inflammation; adding 1-3% fat or oil to feed can reduce dust by 30-50% by binding fine particles.
Maintaining relative humidity between 50-70% is critical; high humidity (>70%) exacerbates ammonia production and pathogen survival, while low humidity (<50%) increases dust suspension and respiratory tract dryness.
Hydrogen sulfide, a highly toxic gas (fatal above 300 ppm), is primarily released during manure agitation and collects in low areas, requiring immediate ventilation and evacuation if detected at elevated levels.
Monitoring air quality at pig nose level (6-12 inches for nursery, 18-24 inches for grow-finish) is essential, as measurements at human height yield falsely low gas concentrations.

If you raise pigs, the air your animals breathe matters as much as the feed they eat and the water they drink. Poor air quality in a swine barn can lead to respiratory disease, reduced feed intake, slower growth rates, and higher mortality, especially in nursery and grow-finish pigs. This guide covers the causes of poor air quality in pig barns, how to monitor ammonia and dust levels, step-by-step improvement strategies, common mistakes, and when to call a veterinarian or extension agent. It is written for swine producers, farm managers, and animal care staff who want practical, actionable methods to protect herd health and worker safety.

The information here applies to conventional confinement barns, naturally ventilated hoop barns, and tunnel-ventilated facilities. While some recommendations may need adjustment for your specific setup, the core principles of measurement, ventilation, and management remain the same across production systems.

At a Glance

Ammonia is the most critical gas to monitor in swine barns. Continuous exposure above 10 to 15 ppm can harm pig respiratory health and reduce performance.
Carbon dioxide levels above 3000 ppm indicate inadequate ventilation, even when ammonia appears acceptable.
Relative humidity should stay between 50 and 70 percent. High humidity increases ammonia and dust problems.
Dust control starts with feed management. Adding fat or oil to feed can reduce dust by 30 to 50 percent.
Ventilation is your primary tool. Minimum ventilation rates must be adjusted seasonally and as pigs grow.
Monitor air quality at pig nose level, not at human standing height.
Check ammonia levels daily in winter when ventilation is lowest and the risk of gas buildup is highest.
If pigs show coughing, sneezing, or increased respiratory effort, measure air quality immediately and correct problems before treating individual animals.
Call a veterinarian if respiratory signs persist after you fix ventilation and ammonia problems, or if death loss rises above normal for your stage of production.

Understanding the Air Quality Problem in Swine Barns

Swine barns present unique air quality challenges because of the combination of animals, manure, feed, and building design. Unlike many other livestock operations, pigs are typically housed indoors at high density, which concentrates both heat and airborne contaminants in a relatively small space.

The main air quality concerns in swine barns are ammonia, hydrogen sulfide, carbon dioxide, methane, inhalable dust, and endotoxins. Each of these affects pig health and worker health differently, and each requires a different management approach.

Ammonia in Pig Barns

Ammonia is the most common and most damaging air pollutant in swine facilities. It forms when bacteria break down urea in urine and undigested protein in manure. The enzyme urease, which is present in feces, converts urea to ammonia gas. This process happens continuously whenever manure is present, and it accelerates as temperature and pH rise.

Ammonia is a water-soluble gas that dissolves easily in the moist lining of the respiratory tract. When pigs inhale ammonia, it irritates the mucous membranes of the nose, trachea, and lungs. At low concentrations, this irritation reduces the function of cilia, the tiny hair-like structures that sweep mucus and pathogens out of the airways. With the cilia damaged, bacteria and viruses have an easier path to the lungs.

The effects of ammonia on pigs are dose dependent. Research and field experience show that continuous exposure to ammonia at 25 ppm or higher reduces growth rate and feed efficiency. Even at 10 to 15 ppm, which is common in poorly ventilated barns, ammonia can predispose pigs to respiratory disease, especially when combined with pathogens like Mycoplasma hyopneumoniae or porcine reproductive and respiratory syndrome virus (PRRSV).

Ammonia also harms farm workers. The Occupational Safety and Health Administration (OSHA) sets a permissible exposure limit of 50 ppm over an 8-hour shift, but many workers report eye and nose irritation at levels well below that. Long-term exposure to moderate ammonia levels can cause chronic bronchitis and reduced lung function in people.

Hydrogen Sulfide and Other Gases

Hydrogen sulfide is another gas produced from manure, particularly when manure is agitated or pumped. It has a distinctive rotten egg smell at low concentrations, but at high concentrations it quickly deadens the sense of smell. Hydrogen sulfide is heavier than air, so it collects in pits, sumps, and low areas. It is extremely toxic and can be fatal to both pigs and humans at concentrations above 300 ppm. Agitation of stored manure is the most dangerous time for hydrogen sulfide release.

Carbon dioxide is produced by pig respiration and by manure decomposition. It is not directly toxic at levels typically found in barns, but it is a good indicator of ventilation adequacy. When carbon dioxide levels climb above 3000 ppm, it usually means the ventilation system is not bringing in enough fresh air. This allows other contaminants, including ammonia and pathogens, to accumulate.

Methane is also produced from manure decomposition, but it is not a major health concern at typical barn concentrations. The bigger risk with methane is explosion risk in enclosed manure storage areas, not in the animal living space.

Dust in Swine Barns

Dust in a swine barn is a mixture of feed particles, dried manure, skin cells, hair, mold spores, pollen, and bacteria. The dust particles that matter most for health are the respirable fraction, particles small enough to reach the deep lung. These particles are less than 10 microns in diameter and are invisible to the naked eye.

Dust causes problems in two ways. First, it physically irritates the airways of both pigs and people. Second, it carries bacteria, viruses, and endotoxins. Endotoxins are components of bacterial cell walls that trigger strong inflammatory responses in the lungs. When pigs inhale dust contaminated with endotoxins, they develop lung inflammation that reduces performance and increases susceptibility to disease.

The main sources of dust in a swine barn are feed, especially ground and pelleted feed, and the pigs themselves. Pigs are active animals that generate dust as they move, root, and interact. The highest dust levels occur during feeding times and during pig movement.

The Interaction Between Ammonia, Dust, and Humidity

Ammonia and dust do not act independently. Dust particles absorb ammonia and other gases, making them heavier and more irritating to the lungs. High humidity makes dust particles stick together and settle, which sounds good, but it also increases ammonia release from manure and creates conditions where bacteria and molds thrive.

The result is that air quality problems tend to compound. A barn with poor ventilation has high humidity, which increases ammonia production. The ammonia irritates pig airways, causing coughing and sneezing. The coughing and sneezing generate more aerosolized pathogens. The dust carries those pathogens through the barn. Within days, a minor air quality problem can become a respiratory disease outbreak.

Monitoring Swine Barn Air Quality

You cannot improve what you do not measure. Regular monitoring of air quality is the foundation of a respiratory health program in swine barns. The goal is to detect problems early, before they affect pig performance or health.

What to Measure

The four most important parameters to monitor are ammonia, carbon dioxide, temperature, and relative humidity. Hydrogen sulfide should be monitored during manure agitation and in barns with deep pit storage. Dust levels should be assessed when respiratory problems persist despite acceptable gas levels.

Ammonia is the priority. Measure it at pig nose level, which is 6 to 12 inches above the floor for nursery pigs and 18 to 24 inches for grow-finish pigs. Ammonia is lighter than some other gases but still stratifies in the barn. Measuring at human head height will give you falsely low readings.

Carbon dioxide is a useful indicator of ventilation rate. Measure it in the center of the barn at pig level. Levels below 1500 ppm indicate generous ventilation. Levels between 1500 and 3000 ppm are acceptable in most seasons. Levels above 3000 ppm mean you need to increase air exchange.

Temperature and humidity should be measured continuously with a digital sensor. These readings help you interpret gas measurements. For example, high ammonia on a cold day points to inadequate minimum ventilation. High ammonia on a warm day points to manure management problems.

Monitoring Methods and Equipment

Several tools are available for measuring barn air quality. The right choice depends on your budget and your goals.

Colorimetric gas detection tubes are the most affordable option for spot checks. These are glass tubes that change color when exposed to a specific gas. You break the ends off the tube, attach it to a hand pump, and draw a measured volume of air through it. The length of the color change indicates the gas concentration. These tubes are accurate enough for routine monitoring and cost a few dollars per tube. They are ideal for weekly checks and for verifying problems detected by other methods.

Electronic gas detectors provide continuous or near-continuous readings. Portable single-gas monitors for ammonia cost between 200 and 500 dollars. They are easy to use and give instant readings. The main drawback is that sensors need periodic calibration and replacement. Most ammonia sensors last 1 to 2 years with proper care.

Multigas monitors measure ammonia, carbon dioxide, hydrogen sulfide, and oxygen in one unit. These cost more, usually 800 to 2000 dollars, but they are valuable for farms with deep pit manure storage or a history of respiratory problems. They also protect workers during manure agitation.

Dust monitoring is more complex. The gold standard is a gravimetric sampler that collects dust on a filter over several hours, which is then weighed in a laboratory. This is expensive and slow, but it is the only accurate way to measure respirable dust. For routine use, a simple light-scattering photometer gives a real-time relative dust reading. These cost 1000 to 3000 dollars. If you cannot afford a dust meter, use visual indicators. Shine a flashlight across the barn at pig level. If you can see dust particles in the beam, dust levels are too high.

How Often to Monitor

Monitor ammonia and carbon dioxide at least weekly in all seasons. In winter, when ventilation is at minimum, check daily. Also check after any ventilation system change, after manure handling, and whenever pigs show respiratory signs.

Monitor temperature and humidity continuously with a recording sensor. Review the data weekly to identify trends. A slow rise in average humidity over several weeks often signals a ventilation problem that is not yet visible.

Monitor hydrogen sulfide whenever you agitate or pump manure. Use a personal monitor worn by the worker doing the agitation. Keep pigs out of the barn during agitation whenever possible. If pigs must remain, ventilate at maximum for at least 30 minutes before agitation and continue during the process.

Recording and Interpreting Data

Keep a simple log of your air quality measurements. Record the date, time, outside temperature, barn temperature, humidity, ammonia level, carbon dioxide level, ventilation stage, and pig age and weight. This log helps you spot patterns and provides valuable information if you need to call a veterinarian.

A simple spreadsheet works well. Create columns for each parameter and add a notes column for observations like "pigs coughing" or "feed delivery day." Review the log monthly to identify trends.

Interpret your readings against these action thresholds:

Ammonia below 10 ppm is acceptable. Continue routine monitoring. Ammonia at 10 to 15 ppm warrants attention. Increase ventilation if possible, check manure management, and recheck within 24 hours. Ammonia above 15 ppm requires immediate action. Increase ventilation, clean manure, and identify the cause. If ammonia exceeds 25 ppm, treat it as a health emergency for both pigs and workers.

Carbon dioxide below 3000 ppm is acceptable. Above 3000 ppm indicates insufficient ventilation regardless of ammonia levels. Increase minimum ventilation and recheck.

Relative humidity below 70 percent is acceptable. Above 70 percent increases ammonia and pathogen survival. Increase ventilation and check drinkers for leaks.

Temperature should stay within the thermoneutral zone for the age of pig. Chilled pigs eat more feed for maintenance and gain slower. Heat-stressed pigs reduce feed intake. Both conditions worsen the effects of poor air quality.

Improving Air Quality Through Ventilation

Ventilation is the most important tool you have for controlling barn air quality. It does three jobs at once. It removes contaminated air, brings in fresh air, and controls temperature and humidity. A well-designed and properly managed ventilation system can keep ammonia below 10 ppm even in cold weather.

Understanding Ventilation Principles

Swine barn ventilation works on the principle of air exchange. Fans exhaust air from the barn, creating a slight negative pressure. Fresh air enters through inlets that are designed to direct incoming air across the ceiling, where it mixes with warm barn air before falling to pig level.

The key to good ventilation is not just moving air, it is mixing air. Cold incoming air is heavier than warm barn air. If it falls directly to the floor, it chills the pigs and fails to mix with contaminated air. Properly designed inlets direct the incoming air upward so it mixes with warm air at the ceiling before dropping to pig level.

Ventilation systems operate in stages. Stage 1, minimum ventilation, runs continuously to control moisture and gases. Stage 2 provides additional air exchange as temperatures rise. Stage 3 and higher provide maximum air movement for heat control. Each stage should be triggered by temperature settings, and the transition between stages should be smooth to avoid drafts.

Setting Minimum Ventilation Rates

Minimum ventilation is the amount of air exchange needed to control moisture and gases without over-cooling the barn. It is expressed in cubic feet per minute (CFM) per pig or per 100 pounds of body weight.

As a general guide, provide 2 to 5 CFM per nursery pig, 10 to 20 CFM per grow-finish pig, and 20 to 35 CFM per finishing pig at weights above 200 pounds. These are minimums. You will need more ventilation as outside temperature rises.

The correct minimum ventilation rate depends on several factors. Cold weather demands lower rates to preserve heat. High humidity demands higher rates to remove moisture. Larger pigs produce more moisture and more ammonia, so they need more air exchange per pig.

Set your minimum ventilation timer to run the first stage fan continuously. If your controller uses a duty cycle, set it so the fan runs at least 30 percent of the time in winter. Check that the fan actually moves the rated air volume. Belts slip, blades collect dust, and shutters stick. A fan that looks like it is running may be moving half its rated airflow.

Seasonal Adjustments

Ventilation needs change dramatically with the seasons, and your monitoring data should drive those changes.

In winter, the goal is to remove moisture and gases while preserving heat. Run minimum ventilation continuously. The most common mistake is turning ventilation down too low to save fuel. This saves a few dollars in propane but costs far more in reduced pig performance and increased medication costs.

In spring and fall, temperatures fluctuate widely between day and night. Use the ventilation controller to transition between stages automatically. This is a time when manual adjustment often fails. A controller that responds to temperature changes is essential.

In summer, the goal is maximum air movement for heat removal. Run all fans at full capacity. Use tunnel ventilation if you have it. High air speed across the pigs helps them cope with heat, but it also increases dust movement. Pay attention to dust control during hot weather.

Common Ventilation Problems and Fixes

Poor air mixing is the most common ventilation problem. Air enters through inlets and falls immediately to the floor, chilling pigs and leaving the upper part of the barn stagnant. Fix this by adjusting inlet openings so that air velocity through the inlet is 500 to 800 feet per minute. Inlets that are too small create high velocity and drafts. Inlets that are too large allow air to fall before mixing.

Static pressure problems cause uneven air distribution. The barn should maintain a static pressure of 0.05 to 0.10 inches of water column. If static pressure is too low, air enters through uncontrolled openings like cracks and gaps, bypassing the inlets. Seal all unintended openings in the building envelope.

Fan maintenance is critical. Clean fan blades and shutters monthly. Check belts for tension and wear. Replace fan belts at least annually. Verify that shutters open fully when fans run. A fan with a stuck shutter can burn out the motor.

Air inlet maintenance matters too. Inlets that are blocked by insulation, dust, or bird nests reduce airflow. Check inlets monthly and clean them as needed.

Managing Manure to Reduce Ammonia

Ventilation removes ammonia, but it cannot keep up with a barn where manure is allowed to accumulate and decompose. Manure management is the second pillar of ammonia control.

How Manure Produces Ammonia

Ammonia forms when urease enzymes in feces break down urea in urine. This reaction happens quickly, within hours of manure deposition. The rate of ammonia release depends on temperature, pH, moisture, and surface area. Warm, wet, alkaline conditions maximize ammonia production.

The practical implication is that fresh manure produces ammonia almost immediately. You cannot wait until the pit is full to address ammonia. You must manage manure continuously to minimize the surface area exposed to air and to remove it regularly.

Flush Systems

Flush systems use water to remove manure from shallow gutters on a regular schedule. Flushing every 2 to 4 hours keeps manure from accumulating and dramatically reduces ammonia levels. The flushed manure goes to a lagoon or storage pond.

Flush systems work best with slatted floors and shallow gutters. The key to success is frequency. Flushing once a day is not enough. Ammonia starts forming within hours, so flush at least every 4 hours during warm weather.

The downside of flush systems is water usage and the need for a lagoon or storage system. If you already have a flush system, check that the flush volume is adequate. A flush that does not completely clean the gutter leaves manure behind and does little for ammonia control.

Deep Pit Storage

Deep pits store manure under the barn for 6 to 12 months. This system is common in the Midwest and other colder regions. Deep pits concentrate ammonia because the manure surface is always present under the slatted floor.

To control ammonia in a deep pit barn, keep the pit as empty as practical. Pumping more frequently, such as every 3 to 4 months instead of annually, reduces the manure surface area and lowers ammonia levels. Coordinate pumping with crop needs for fertilizer.

Pit additives are marketed as ammonia reducers. Some products contain urease inhibitors that slow the conversion of urea to ammonia. Research results are mixed. Some products reduce ammonia for a few weeks, but none eliminate the need for ventilation and frequent manure removal. If you use a pit additive, continue monitoring ammonia to verify it works on your farm.

Bedding Management

Barns using deep bedding or hoop structures have different ammonia dynamics. The bedding absorbs urine, and the carbon in the bedding helps tie up nitrogen. However, if bedding becomes wet and packed, it becomes anaerobic and produces ammonia and other gases.

The key to ammonia control in bedded systems is adding fresh bedding regularly and removing wet, packed material. The carbon-to-nitrogen ratio of the bedding matters. High-carbon bedding like straw or wood shavings absorbs more urine and reduces ammonia release compared to low-carbon materials like sawdust from softwoods.

Scraping and Cleaning

In barns with solid floors, scrape manure at least daily, and ideally twice daily. Scraping removes the source of ammonia before bacteria can convert it to gas. Combine scraping with a dry cleaning method rather than washing. Washing adds moisture, which increases ammonia production and humidity.

If you wash alleys or pens, do it when the barn is empty between groups. During occupancy, use scraping and minimal water.

Controlling Dust in Swine Barns

Dust control requires a different set of tools than gas control. Ventilation helps remove dust, but it also stirs it up. The most effective dust control strategies reduce dust at the source.

Feed Management for Dust Control

Feed is the largest source of dust in most swine barns. Ground feed, especially finely ground corn and soybean meal, produces fine particles that become airborne when feed is delivered, when pigs eat, and when they root in feeders.

Adding fat or oil to feed at 1 to 3 percent reduces dust by binding fine particles. This is one of the most cost-effective dust control measures available. The fat also improves feed palatability and reduces feed wastage. Common options include choice white grease, soybean oil, or distillers corn oil.

Feed form matters. Pellets produce less dust than meal. If you feed meal, consider increasing particle size slightly. Feed particles that are too fine are more likely to become airborne and more likely to cause respiratory irritation. A target particle size of 600 to 800 microns balances feed efficiency with dust control.

Feed delivery is a high-dust event. Fill feeders carefully to minimize spillage. Use auger systems with drop chutes that minimize the distance feed falls. Clean up spilled feed promptly. Feed left on the floor is walked on, ground into dust, and becomes airborne.

Water and Oil Spray Systems

Misting systems that spray a fine mist of water or oil into the barn air can reduce dust significantly. Water misters work by making dust particles heavier so they settle. Oil misters work by making dust particles stick to surfaces instead of remaining airborne.

Water misting works best in hot weather when the added humidity is not a problem. In cool weather, misting increases humidity and ammonia, which trades one problem for another. Use water misting only when temperatures are above 70 degrees Fahrenheit.

Oil misting with a light mineral oil or canola oil can reduce airborne dust by 50 to 70 percent. The oil is applied as a fine mist from nozzles mounted near the ceiling. Oil misting works in all seasons because it does not add moisture. The main drawbacks are the cost of oil and the need to clean oil-coated surfaces periodically.

Managing Pig Activity

Pig activity is a major driver of dust levels. Dust levels spike during feeding, when pigs are disturbed, and when they are moved. You cannot eliminate pig activity, but you can manage it.

Feed at consistent times so pigs anticipate feeding and are less frantic. Avoid unnecessary disturbance during rest periods. When moving pigs, move them calmly and efficiently. Each disturbance event sends a wave of dust into the air that takes 30 minutes or more to settle.

Filtration and Air Cleaning

In severe cases, or in barns with high-value animals like breeding stock, you may consider air filtration. High-efficiency particulate air (HEPA) filters can remove almost all dust particles, but they require substantial investment in equipment and energy. Less expensive panel filters can remove larger particles and reduce dust load.

Air filtration is most practical for boar studs and high-health nursery facilities where the cost of excluding pathogens is justified. For most grow-finish barns, source control and ventilation are more cost-effective.

Managing Humidity for Better Air Quality

Humidity ties together many air quality problems. High humidity increases ammonia production, increases dust stickiness, and promotes pathogen survival. Low humidity increases dust suspension and dries out pig mucous membranes, making them more susceptible to infection.

The target range is 50 to 70 percent relative humidity. Below 50 percent, dust becomes a bigger problem. Above 70 percent, ammonia and pathogens become bigger problems.

Sources of Humidity

Pigs produce significant moisture through respiration and manure. A 150-pound pig produces about 1.5 gallons of water vapor per day. A barn with 1000 grow-finish pigs produces 1500 gallons of moisture daily. This moisture must be removed by ventilation.

Other sources of humidity include leaking drinkers, wet cleaning, and poorly managed manure. A leaking nipple drinker can add gallons of water to the pit or floor daily. Check drinkers regularly and repair leaks promptly.

Controlling Humidity

Ventilation is the primary tool for humidity control. The minimum ventilation rate should be set to remove moisture. If humidity stays above 70 percent with the minimum ventilation running, increase the ventilation rate.

Reduce moisture sources. Fix leaking drinkers. Use dry cleaning methods during occupancy. Keep manure surfaces as small as possible. In bedded systems, add fresh bedding to absorb moisture.

In winter, the challenge is removing moisture without losing too much heat. This is why minimum ventilation must run continuously, even on the coldest nights. A barn that is sealed tight to save heat will quickly develop high humidity and high ammonia.

Common Mistakes in Air Quality Management

Even experienced producers make mistakes with air quality. Recognizing these common errors can help you avoid them.

Measuring Ammonia at the Wrong Height

Ammonia is often measured at human head height, which gives lower readings than what pigs experience. Always measure at pig nose level. The difference can be 5 to 10 ppm or more.

Relying on Smell

Your nose is not a reliable ammonia detector. At low concentrations, ammonia smell is not always noticeable. At higher concentrations, the sense of smell quickly becomes fatigued, and you stop noticing the odor. By the time you can smell ammonia strongly, levels are likely above 25 ppm. Use a gas detector tube or electronic monitor instead.

Turning Down Ventilation to Save Money

Reducing ventilation in winter saves fuel but costs far more in pig performance and health. The feed cost of reduced growth and the medication cost of respiratory disease far exceed the fuel savings. Run minimum ventilation continuously.

Ignoring Carbon Dioxide

Many producers monitor ammonia but ignore carbon dioxide. Carbon dioxide is an excellent indicator of ventilation adequacy. If carbon dioxide is above 3000 ppm, ventilation is insufficient even if ammonia seems acceptable. Measure both gases.

Cleaning With High-Pressure Water During Occupancy

High-pressure washing during occupancy adds enormous amounts of moisture and stirs up pathogens. Use dry cleaning methods while pigs are in the barn. Save high-pressure washing for between groups when the barn is empty.

Not Maintaining Fans

A fan that looks like it is running may be moving half its rated airflow. Dirty blades, loose belts, and stuck shutters reduce airflow. Clean and inspect fans monthly. Replace belts annually.

Forgetting About Seasonal Changes

Ventilation settings that work in October will not work in January or April. Review your ventilation settings monthly and adjust based on temperature trends and air quality measurements.

When to Call a Veterinarian or Extension Agent

Air quality monitoring and improvement is something you can do yourself, but there are times when you need professional help.

Signs That Air Quality Is Causing Health Problems

If you see any of the following signs, measure air quality immediately and correct any problems you find. If the signs persist after correction, call a veterinarian.

Pigs coughing, sneezing, or showing increased respiratory effort are the most obvious signs. A sudden increase in the number of pigs requiring antibiotic treatment for respiratory disease is another warning sign. Reduced feed intake, slower growth, and increased variability in pig weights can all indicate chronic air quality problems.

Eye irritation in pigs, seen as reddened or swollen eyes, is a specific sign of ammonia exposure. If you see eye irritation in multiple pigs, check ammonia levels immediately.

When to Call a Veterinarian

Call a veterinarian if respiratory signs persist for more than 48 hours after you have corrected identified air quality problems. Also call if death loss rises above normal for your stage of production, if multiple pigs show severe respiratory distress, or if you suspect a specific disease like PRRSV or influenza.

Your veterinarian can perform diagnostic testing to identify the pathogens involved. They can also recommend treatment protocols and vaccination strategies. Do not delay calling. Early intervention reduces both pig suffering and financial loss.

When to Call an Extension Agent

Call your local cooperative extension agent or swine specialist when you need help with ventilation system design or troubleshooting. Extension agents can help you calculate ventilation rates, evaluate inlet placement, and design monitoring programs. They often have access to specialized equipment like airflow meters and thermal imaging cameras.

Extension agents are also excellent resources for training your staff on air quality monitoring. Many extension programs offer workshops and online resources on swine barn ventilation and air quality.

Emergency Situations

Some air quality situations require immediate evacuation of both pigs and people. If you detect hydrogen sulfide at levels above 10 ppm during manure agitation, stop the agitation, ventilate at maximum, and evacuate the barn. If a worker experiences dizziness, headache, or loss of consciousness in a barn, evacuate immediately and call emergency services.

If pigs show signs of acute gas poisoning, such as gasping, staggering, or collapse, open all doors and curtains, turn on all fans, and remove affected pigs to fresh air. Call a veterinarian immediately.

Developing a Year-Round Air Quality Plan

A written air quality plan helps you stay consistent and catches problems before they become serious. Your plan should cover monitoring schedules, ventilation settings, manure management, and emergency procedures.

Monthly Monitoring Schedule

Check ammonia and carbon dioxide at least weekly. In winter, check daily. Record all readings in your log.

Clean and inspect fans monthly. Check belts, blades, and shutters. Verify that fans are moving air by feeling the airflow at the exhaust.

Check inlets monthly. Remove dust and debris. Verify that inlets open and close properly.

Check drinkers monthly for leaks. Fix any leaks you find. A dripping drinker adds moisture and promotes ammonia.

Seasonal Checklists

In fall, before cold weather arrives, test all heating and ventilation equipment. Clean fans and replace belts. Calibrate thermostats and controllers. Check that emergency ventilation systems work.

In spring, as temperatures rise, transition from minimum to higher ventilation stages. Clean dust from fans and inlets. Check that summer ventilation equipment, such as tunnel fans and evaporative cooling pads, is ready.

In summer, monitor for heat stress in addition to air quality. Provide extra ventilation during the hottest part of the day. Watch for dust problems during dry periods.

In winter, run minimum ventilation continuously. Check ammonia daily. Watch for ice buildup on inlets and fans. Ensure that emergency ventilation can operate even in extreme cold.

Staff Training

Everyone who works in the barn should understand the basics of air quality monitoring. Train staff to use gas detection tubes and electronic monitors. Teach them the action thresholds for ammonia and carbon dioxide. Show them how to check fans and inlets for problems.

Post a simple action chart in the barn that lists what to do at each ammonia level. Include emergency procedures for hydrogen sulfide detection and gas exposure.

Frequently Asked Questions

What is a safe ammonia level for pigs?

Ammonia levels below 10 ppm are generally safe for pigs. Levels between 10 and 15 ppm can harm respiratory health, especially in young pigs or during disease challenges. Levels above 25 ppm are clearly harmful and require immediate correction. The goal should be to keep ammonia below 10 ppm at pig nose level at all times.

How often should I check ammonia levels in my pig barn?

Check ammonia at least weekly in all seasons. In winter, when ventilation is at minimum, check daily. Also check after any change to the ventilation system, after manure handling, and whenever pigs show respiratory signs. Regular monitoring is the only way to catch problems before they affect pig health.

Can I use my sense of smell to detect ammonia problems?

No. Your nose is not a reliable ammonia detector. At low concentrations, ammonia smell may not be noticeable. At higher concentrations, your sense of smell becomes fatigued and you stop noticing the odor. By the time you can smell ammonia strongly, levels are likely above 25 ppm. Use a gas detection tube or electronic monitor instead.

What causes high ammonia levels in a pig barn?

High ammonia is caused by the breakdown of urea in urine by urease enzymes in feces. The main contributing factors are inadequate ventilation, infrequent manure removal, high humidity, and warm temperatures. High stocking density and poor feeder management also contribute because they increase the amount of manure produced per unit of barn space.

How do I reduce dust in my swine barn?

The most effective dust control methods are adding fat or oil to feed at 1 to 3 percent, feeding pellets instead of meal, using oil misting systems, and managing pig activity to reduce disturbance. Ventilation helps remove dust but does not reduce dust production. Focus on reducing dust at the source.

What is the best way to measure ammonia in a barn?

Colorimetric gas detection tubes are the most affordable and accurate option for spot checks. Electronic ammonia monitors provide continuous readings and are worth the investment for larger operations. Whichever method you use, measure at pig nose level, not at human standing height. Ammonia levels are higher near the floor.

How does humidity affect air quality in a pig barn?

High humidity above 70 percent increases ammonia production from manure and promotes the survival of pathogens in the air. Low humidity below 50 percent increases dust suspension and dries out pig mucous membranes. The target range is 50 to 70 percent relative humidity.

When should I call a veterinarian about air quality problems?

Call a veterinarian if respiratory signs in pigs persist for more than 48 hours after you have corrected identified air quality problems, if death loss rises above normal, or if you suspect a specific disease like PRRSV or influenza. Do not wait to see if the problem resolves on its own. Early intervention reduces both pig suffering and financial loss.

Related Farming Guides

This section will be populated with links to related farming guides after publication. Check back for additional resources on swine health, ventilation system design, and respiratory disease prevention.

Related Clinical & Scientific Guides

References

National Pork Board: https://www.pork.org/
USDA APHIS Swine Health: https://www.aphis.usda.gov/livestock-poultry-disease/swine
FAO Pig Production: https://www.fao.org/pig-production-and-products/en/
FAO Animal Production and Health: https://www.fao.org/animal-production/en/
WOAH (World Organisation for Animal Health): https://www.woah.org/en/home/

This article is educational and is not a substitute for veterinary diagnosis, treatment, public-health guidance, or regulatory reporting.