Dairy Cow Barn Air Quality Management for Respiratory and Udder Health

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

Key Takeaways

Ammonia levels exceeding 10-15 ppm are detrimental to dairy cow respiratory health, damaging cilia and increasing susceptibility to bacterial pneumonia by pathogens like Mannheimia haemolytica and Histophilus somni.
Respirable dust particles (<10 microns) bypass upper airway defenses, settling deep in the lungs, triggering allergic responses, and facilitating direct bacterial entry, necessitating control of feed, bedding, and dried manure sources.
High barn humidity (>70%) promotes bacterial growth in bedding, increasing teat-end exposure to environmental mastitis pathogens such as E. coli and Klebsiella, while also stressing the cow's immune system.
Effective ventilation requires airflow rates of 500-700 CFM/cow in summer and 100-200 CFM/cow in winter, with critical air movement (2-5 mph airspeed in summer) at cow level to remove contaminants and facilitate cooling.
Ammonia is best controlled at the source through frequent manure removal (at least twice daily scraping) and proper bedding management to minimize urine contact with air and bacterial decomposition.
Weekly monitoring of ammonia levels using gas detection tubes or electronic sensors, alongside visual dust assessments and bedding moisture checks, is crucial for early detection and prevention of health issues.

Poor air quality inside a dairy barn does more than make the environment uncomfortable. It directly harms the respiratory tract of your cows, weakens their immune defenses, and creates conditions where mastitis-causing bacteria thrive. This guide explains how to diagnose, fix, and prevent air quality problems in your barn. It covers ammonia and dust control, ventilation system design, seasonal management adjustments, and monitoring strategies. It is written for dairy producers, herd managers, and farm employees who want practical solutions they can apply today.

At a Glance

Ammonia is your first warning sign. If you can smell ammonia, levels are likely above 10 to 15 ppm, which is too high for cow health.
Ventilation rate matters more than fan count. Aim for 500 to 700 cubic feet per minute (CFM) per cow in summer and 100 to 200 CFM per cow in winter for naturally ventilated barns.
Air movement at cow level is critical. Cows need 2 to 5 mph airspeed in summer to promote cooling and keep stale air away from their faces.
Dust and ammonia work together. Dust particles carry ammonia and bacteria deep into the lungs, so controlling one without the other is ineffective.
Bedding choice affects air quality. Sand and straw produce different dust and bacterial loads. Match your bedding to your ventilation capacity.
Monitor weekly, not seasonally. A simple ammonia test strip and a visual dust check take five minutes and catch problems early.
Udder health follows air quality. High ammonia and humidity increase teat-end exposure to environmental bacteria like E. coli and Klebsiella.

Understanding the Air Quality Problem in Dairy Barns

The air inside a dairy barn is a mixture of gases, dust particles, moisture, and microorganisms. When cows are confined, this mixture becomes concentrated. Each cow exhales moisture and carbon dioxide, produces manure that releases ammonia, and sheds hair and skin cells that become dust. The result is a complex pollution load that your ventilation system must remove continuously.

The three main contaminants you need to manage are ammonia, dust, and moisture. Each one has a different source and a different effect on cow health.

Ammonia comes from the breakdown of urea in urine and from manure decomposition. It is a colorless gas with a sharp, pungent smell. When ammonia dissolves in the moisture on the mucous membranes of the respiratory tract, it forms ammonium hydroxide, which is caustic. This damages the cilia, the tiny hair-like structures that line the airways and sweep mucus and trapped particles out of the lungs. When cilia are damaged, bacteria and dust stay in the lungs longer and cause more damage.

Dust in a dairy barn comes from feed, bedding, dried manure, hair, and pollen. The particles that matter most for health are the small ones, those under 10 microns in diameter. These particles, called respirable dust, bypass the upper airway defenses and settle deep in the lungs. They can trigger allergic responses, reduce lung function, and carry bacteria directly into the respiratory system.

Moisture is less obvious but equally important. High humidity makes the air feel heavy and reduces the effectiveness of evaporative cooling in summer. It also keeps bedding damp, which promotes bacterial growth. Wet bedding directly increases the bacterial load on teat ends and raises the risk of environmental mastitis.

The relationship between these three contaminants is what makes barn air quality a systems problem. Ammonia adsorbs onto dust particles, so dusty barns often have high ammonia concentrations even when ventilation seems adequate. Moisture makes dust heavier and more likely to settle on surfaces, but it also makes bedding a bacterial reservoir. You cannot solve one problem without addressing the others.

How Air Quality Affects Respiratory Health

The respiratory tract of a cow is a continuous surface from the nostrils to the alveoli. It has defense mechanisms at every level, but those defenses have limits. When the air a cow breathes is loaded with ammonia, dust, and pathogens, the defenses become overwhelmed.

The first sign of respiratory irritation is often a mild cough or increased nasal discharge. This is the cow's body trying to remove irritants. As exposure continues, the cilia in the airways become paralyzed or destroyed. Mucus production increases, but without functional cilia, the mucus pools in the airways. This creates a warm, moist environment where bacteria multiply.

The bacteria that cause bovine respiratory disease, including Mannheimia haemolytica, Pasteurella multocida, and Histophilus somni, are often present in small numbers in the upper airways of healthy cattle. When the defense mechanisms are damaged, these bacteria move down into the lungs and cause pneumonia. This is why respiratory disease outbreaks often follow periods of poor air quality.

The economic impact of respiratory disease goes beyond treatment costs. Affected cows eat less, gain less weight if they are growing, and produce less milk if they are lactating. In severe cases, lung damage is permanent, and the cow never reaches her full production potential.

How Air Quality Affects Udder Health

The connection between air quality and mastitis is less direct than the connection to respiratory disease, but it is just as important. Mastitis is an infection of the mammary gland, and the bacteria that cause it come from the environment or from other cows. Air quality influences both sources.

Environmental mastitis pathogens, especially E. coli and Klebsiella, live in manure, soil, and contaminated bedding. High humidity in the barn keeps bedding wet, and wet bedding supports bacterial growth. A cow lying in wet, contaminated bedding has teat ends constantly exposed to bacteria. High ammonia levels in the air can also irritate the teat end, making it easier for bacteria to enter the teat canal.

Poor air quality also stresses the cow's immune system. When a cow is stressed, cortisol levels rise, and immune function declines. This means that even if the bacterial challenge is the same, a cow in a poorly ventilated barn is more likely to develop a clinical infection than a cow in a well-ventilated barn.

The relationship between bedding moisture and mastitis is well documented. The National Mastitis Council recommends that bedding be kept as dry as possible to minimize bacterial growth. Air quality is a major factor in bedding moisture. If your ventilation system cannot remove the moisture produced by the cows, your bedding will stay wet no matter how often you add fresh material.

Diagnosing Your Barn's Air Quality

Before you can fix an air quality problem, you need to know what you are dealing with. The first step is a systematic walkthrough of your barn. Do this on a day when the barn is full and the weather is typical for the season. A walkthrough on a windy spring day will not tell you what your cows experience on a calm, humid summer night.

Start at the cow level. Crouch down so your face is at the height of a cow's head when she is lying down. Take several slow breaths. What do you smell? If you detect ammonia, the level is at least 5 to 10 ppm. If your eyes water or your throat feels irritated, the level is above 15 to 20 ppm. These are not safe levels for cows.

Next, look up at the ceiling and along the ridge. Look for cobwebs, dust accumulation, and condensation. Cobwebs indicate that air is not moving through the barn. Dust accumulation on horizontal surfaces means the air is not carrying particles out of the building. Condensation on the ceiling or walls means the humidity is too high.

Check the bedding. Pick up a handful and squeeze it. If water drips out, the bedding is too wet. If it forms a ball that holds its shape, it is borderline. If it crumbles and falls apart, it is dry enough for good udder health.

Look at the cows themselves. Are they breathing rapidly at rest? Do you see nasal discharge or excessive drooling? Are there multiple cows coughing? These are signs that the air quality is already affecting their health.

Finally, check your ventilation system. Are all fans running? Are the air inlets open? Is the ridge vent clear of debris and bird nests? Many air quality problems are simply the result of a blocked inlet or a broken fan that no one noticed.

Measuring Ammonia Levels

Your nose is a useful tool, but it is not precise. For accurate ammonia monitoring, use a gas detection tube or an electronic sensor. Gas detection tubes are inexpensive and easy to use. You break the ends off a glass tube, attach it to a hand pump, and draw a measured volume of air through the tube. The tube changes color along a scale, and you read the concentration directly.

Electronic ammonia sensors are more expensive but provide continuous monitoring. They are useful if you have had chronic problems or if you want to track ammonia levels over time. Place the sensor at cow level, not near the ceiling, because ammonia is lighter than air and concentrations vary with height.

Test at multiple locations in the barn. Ammonia levels are rarely uniform. The highest concentrations are usually found in the most poorly ventilated areas, such as corners, behind solid partitions, and near the manure alleys. Test at the beginning of the day before ventilation systems have had a chance to remove the overnight accumulation, and again in the afternoon.

The target is less than 10 ppm at cow level. Levels above 25 ppm require immediate action. If you measure levels above 10 ppm, your ventilation is inadequate or your manure management is not keeping up with production.

Measuring Dust Levels

Dust is harder to measure precisely than ammonia because it varies in particle size and composition. For a practical farm assessment, you have two options.

The first is a visual assessment. Shine a flashlight beam across the barn at cow level. If you can see dust particles floating in the beam, the dust load is high. If the beam looks clear, the air is relatively clean. This is not a precise measurement, but it is a useful screening tool.

The second option is a dust monitor. These devices draw a known volume of air through a filter, and the filter is weighed before and after sampling to determine the dust concentration. They are more expensive and require more training to use, but they give you a reliable number. The target for respirable dust in a dairy barn is less than 2.5 milligrams per cubic meter.

If you do not have access to a dust monitor, use the visual assessment and pay attention to the source of the dust. Feed alleys, bedding storage, and dry, dusty paddocks are common sources. If you can see dust coming from a specific source, address that source first.

Ventilation System Design Principles

Ventilation is the primary tool for managing barn air quality. The goal is to remove contaminated air and replace it with fresh air from outside. There are two main types of ventilation systems: natural and mechanical.

Natural ventilation relies on wind and thermal buoyancy to move air through the barn. Open ridge vents allow warm, moist air to rise and escape, while sidewall openings allow fresh air to enter. Natural ventilation works well in mild climates and in barns with open sidewalls. It is less effective on calm days and in cold weather when sidewalls are closed to protect cows from drafts.

Mechanical ventilation uses fans to move air. There are two subtypes: tunnel ventilation and cross ventilation. Tunnel ventilation places fans at one end of the barn and air inlets at the other end, creating a continuous flow of air down the length of the barn. Cross ventilation places fans and inlets on opposite sidewalls, moving air across the width of the barn.

The ventilation rate you need depends on the season and the number of cows. In summer, you need enough airflow to remove body heat and support evaporative cooling. In winter, you need enough airflow to remove moisture and ammonia without creating drafts that chill the cows.

For naturally ventilated barns, the summer ventilation rate should be 500 to 700 CFM per cow. The winter rate should be 100 to 200 CFM per cow. For mechanical systems, the design should provide at least 800 CFM per cow in summer for tunnel ventilated barns.

The key to effective ventilation is not just the total airflow but the distribution of that airflow. Air must reach cow level, where the cows are. Stagnant zones, where air does not move, are where ammonia and dust accumulate. These zones are often found in corners, behind solid partitions, and in areas where the building geometry creates pockets of still air.

Natural Ventilation Improvements

If your barn relies on natural ventilation, the first thing to check is the ridge opening. The ridge should be open and unobstructed for the full length of the barn. The width of the opening should be at least 2 inches for every 10 feet of building width. A 60-foot-wide barn needs a ridge opening of at least 12 inches.

The sidewalls should be open enough to allow air to enter. In summer, the sidewalls should be fully open. In winter, you can close them partially, but you need to leave enough opening for ventilation. A common mistake is closing the sidewalls too much in winter to keep the barn warm, which traps ammonia and moisture inside.

The orientation of the barn relative to prevailing winds matters. The open side of the barn should face the prevailing summer wind. If your barn is oriented wrong, you can add windbreaks or deflectors to redirect airflow, but it is much easier to design the barn correctly from the start.

If natural ventilation is not providing enough air movement, you can add mechanical assistance. Stirring fans mounted on the trusses can keep air moving even on calm days. These fans do not bring fresh air into the barn, but they mix the air and prevent stagnant zones from forming.

Mechanical Ventilation Improvements

Mechanical ventilation systems need regular maintenance to work properly. Fans lose efficiency as dust accumulates on the blades and the motor housing. The fan blades should be cleaned at least monthly during periods of heavy use. Check the belts for wear and tension. A loose belt reduces fan speed and airflow.

The air inlets are just as important as the fans. Inlets must be sized and positioned to distribute air evenly across the barn. If the inlets are too small, the fans will create negative pressure that pulls air through cracks and gaps, creating drafts. If the inlets are too large, the air will not reach the center of the barn.

In tunnel ventilated barns, the inlet area should be sized so that the air velocity through the inlet is between 500 and 700 feet per minute. You can calculate the required inlet area by dividing the total fan capacity in CFM by the desired inlet velocity. For example, a barn with 100,000 CFM of fan capacity needs an inlet area of 143 to 200 square feet.

Check the fans for proper operation. A fan that is running but not moving air, because the blades are reversed or the belt is slipping, is wasting electricity and not helping your cows. Use a piece of string or a thin ribbon to check air movement at cow level. The string should be moving steadily, not fluttering or hanging still.

Controlling Ammonia at the Source

Ventilation removes ammonia, but it is more efficient to prevent ammonia from forming in the first place. Ammonia comes from the breakdown of urea in urine, so the key is to keep urine and manure from sitting on surfaces where bacteria can break them down.

The most effective strategy is frequent manure removal. Scrape alleys at least twice a day, and more often in summer when bacterial activity is highest. The longer manure sits, the more ammonia it releases. In slatted floor systems, the pits should be designed to remove manure quickly and prevent the buildup of solids.

Grooved or sloped floors help urine drain away from the cow area. If urine pools on the floor, it releases ammonia continuously. A floor that slopes 1 to 2 percent toward a drain or gutter can significantly reduce ammonia levels.

Bedding management also affects ammonia. Urine soaked into bedding releases ammonia slowly but continuously. If you use organic bedding like straw or sawdust, remove wet spots daily and add fresh bedding. If you use sand, it drains better but can still harbor bacteria if it becomes contaminated with manure.

There are products that can help control ammonia. Acidifying agents, such as those containing sodium bisulfate, lower the pH of the manure and urine, which reduces ammonia volatilization. These products can be applied to stall beds or manure alleys. They are not a substitute for good ventilation and manure removal, but they can help in problem areas.

Controlling Dust at the Source

Dust control starts with identifying the source. In most dairy barns, the main sources are feed, bedding, and dried manure.

Feed dust is a major problem, especially with dry hay and grain. When you feed, dust is released into the air, and it can hang in the air for hours. To reduce feed dust, use a feed that has been processed to reduce fines, such as pellets or cubes. Add a small amount of water or molasses to dusty feed to bind the particles together. Feed in a way that minimizes dropping and scattering.

Bedding dust is also significant, especially when you use sawdust or shavings. When you add new bedding, the dust is released into the air. To reduce bedding dust, consider using a bedding that produces less dust, such as sand or straw. If you must use sawdust, try to add it when the cows are not in the barn, or wet it slightly before spreading.

Dried manure on alley floors and on the cows themselves becomes dust when it is disturbed by cow movement or by fans. Frequent manure removal reduces this source. Grooming cows, either with a mechanical cow brush or by regular brushing, removes dried manure and hair that would otherwise become airborne.

The barn environment itself can generate dust. Hay stored in the barn releases dust as it is handled. Grain bins and feed storage areas release dust when they are filled or emptied. Keep these areas separate from the cow area, or enclose them to contain the dust.

Managing Humidity

Humidity is the hidden factor in barn air quality. High humidity makes ammonia and dust more damaging, and it directly affects bedding moisture and udder health.

Cows produce a large amount of moisture through respiration and urination. A single lactating cow can produce several gallons of water vapor per day. If this moisture is not removed, the humidity in the barn rises.

The relative humidity in a dairy barn should be between 50 and 70 percent. Above 70 percent, bedding begins to stay wet, and bacterial growth increases. Below 50 percent, dust becomes more of a problem because the air is dry and particles stay suspended.

In summer, humidity is often a problem because warm air can hold more moisture. Your ventilation system must remove this moisture. In winter, the problem is different. Cold air holds less moisture, so the humidity in the barn can become very high relative to the outside air. This is why winter ventilation is so important, even though it seems counterintuitive to open the barn when it is cold outside.

One way to manage humidity is to keep the cow areas clean and dry. Scrape alleys regularly, and do not let water accumulate on the floor. Check waterers for leaks and fix them promptly. A leaking waterer can add a significant amount of moisture to the air.

If you use sprinklers or misters for evaporative cooling in summer, make sure they are not overused. The goal is to wet the cows, not the barn. If the sprinklers are running long enough to saturate the bedding, they are doing more harm than good.

Seasonal Air Quality Management

Air quality problems change with the seasons, and your management must change with them.

In summer, the main challenges are heat and humidity. Cows are stressed by heat, and their respiration rate increases, which adds more moisture to the air. The ventilation system must be running at maximum capacity. In naturally ventilated barns, the sidewalls should be fully open. In mechanically ventilated barns, all fans should be running.

Summer is also the season when dust is most likely to be a problem, because dry conditions and increased air movement stir up more particles. Pay extra attention to dust control in summer, and consider using sprinklers or misters to settle dust as well as to cool the cows.

In winter, the main challenge is the conflict between keeping the barn warm and keeping the air fresh. Many producers close the barn up tight to protect the cows from cold, but this traps ammonia, moisture, and dust inside. The result is a barn that is warm but has terrible air quality.

The solution is to ventilate for air quality, not for temperature. Cows are more cold-tolerant than heat-tolerant. A cow can handle a cold draft better than she can handle high ammonia levels. In winter, maintain the minimum ventilation rate to keep ammonia below 10 ppm and humidity below 70 percent, even if this means the barn is cooler than you would like.

Spring and fall are transition seasons, and they are often when air quality problems are most likely to go unnoticed. The weather is mild, so the ventilation system is not running at full capacity, but the cows are still producing moisture and ammonia. Check your ammonia levels regularly during these seasons.

Common Air Quality Mistakes

Many producers make the same mistakes when trying to manage barn air quality. Recognizing these mistakes can help you avoid them.

The first mistake is relying on your nose to detect ammonia. By the time you can smell ammonia, the levels are already too high for the cows. Cows have a more sensitive sense of smell than humans, and they are being affected even when you cannot detect the odor.

The second mistake is overstocking the barn. Every cow adds moisture, heat, ammonia, and dust to the air. If you add more cows than the ventilation system was designed for, air quality will suffer. The ventilation system should be sized for the maximum number of cows you will house in the barn.

The third mistake is ignoring the importance of air distribution. A barn can have plenty of total ventilation capacity but still have stagnant zones where air does not move. These zones are where respiratory and udder health problems will occur. Use smoke tests or string tests to identify stagnant zones and add stirring fans to eliminate them.

The fourth mistake is focusing on ventilation while ignoring manure management. No ventilation system can keep up with a barn that is not cleaned regularly. Manure removal and ventilation are two parts of the same system, and both must be working.

The fifth mistake is not adjusting the ventilation system as the season changes. A system that is set for summer will create drafts in winter. A system that is set for winter will create stagnant conditions in summer. Adjust your inlets, fans, and sidewalls as the weather changes.

Monitoring and Recordkeeping

You cannot manage what you do not measure. A simple monitoring program will help you catch problems before they affect cow health.

Test ammonia levels at least once a week, and more often if you have had problems. Record the levels by location in the barn, so you can identify problem areas. Keep a log of the outside temperature, the weather conditions, and the ventilation settings. This will help you understand how the weather affects your barn's air quality.

Check the ventilation system at least once a week. Look for fans that are not running, belts that are loose, and inlets that are blocked. Clean fan blades and screens as needed. Record any maintenance you perform.

Monitor cow health for signs of respiratory and udder problems. Track the number of cows with coughing, nasal discharge, and elevated respiration rates. Track your somatic cell count (SCC) and clinical mastitis cases. If these numbers start to rise, check your air quality before assuming it is a disease problem.

A simple recordkeeping system can be a notebook or a spreadsheet. The important thing is to be consistent. Record the same measurements at the same time each week, so you can compare data over time.

When to Call a Veterinarian or Extension Agent

You should be able to handle most air quality problems with the strategies in this guide. However, there are times when you need professional help.

Call a veterinarian if you see signs of respiratory disease in multiple cows. Coughing, nasal discharge, fever, and labored breathing are all signs that the cows need medical attention. The veterinarian can diagnose the specific pathogen and recommend treatment. Do not wait until the problem is widespread before calling.

Call a veterinarian if your somatic cell count is rising or if you are seeing more cases of clinical mastitis than usual. The veterinarian can help you determine whether the problem is in the barn environment or in the milking procedure.

Call your local extension agent if you need help designing a ventilation system or if you are planning to remodel or build a new barn. The extension agent can provide guidance on ventilation rates, inlet sizing, and system design. They can also help you interpret your monitoring data and develop a plan for improvement.

Call an extension agent or a ventilation specialist if you have tried to fix an air quality problem and the ammonia levels are still too high. Sometimes the problem is in the building design itself, and it takes a professional eye to identify the issue.

Frequently Asked Questions

What is a safe ammonia level in a dairy barn?

The safe level is below 10 parts per million at cow level. Levels between 10 and 25 ppm cause irritation to the respiratory tract and reduce immune function. Levels above 25 ppm require immediate action. If you can smell ammonia, it is already above the safe level, because human smell detection begins at about 5 to 10 ppm.

How often should I clean the fans in my barn?

Clean the fan blades, shrouds, and screens at least monthly during periods of heavy use. Dust builds up on fan blades and reduces airflow by 20 to 40 percent. A dirty fan moves less air and uses the same amount of electricity. In dusty conditions or during summer when fans run constantly, clean them every two weeks.

Can I use sprinklers to control dust in the barn?

Yes, sprinklers can help settle dust, but use them carefully. Light misting can settle dust without wetting the bedding. Heavy sprinkling will wet the bedding and increase the risk of mastitis. Use sprinklers only in the alleys and cow areas where dust is a problem, and make sure the cows have time to dry before they lie down.

Why is my barn more dusty in winter even though the windows are closed?

Dust accumulates when there is not enough air movement to carry it out of the barn. In winter, when the barn is closed up, the air becomes still, and dust settles on surfaces and hangs in the air. The solution is to maintain a minimum ventilation rate even in winter. Open the ridge vent and leave some sidewall opening to allow moisture and dust to escape.

Does sand bedding produce less ammonia than straw?

Sand bedding produces less ammonia than straw because urine drains through sand more quickly and does not pool on the surface. Straw absorbs urine, holding it in contact with the air where bacteria can break it down and release ammonia. However, sand can be harder on the cows' hocks and requires more frequent replacement. Choose the bedding that works best for your barn and management system.

How does air quality affect mastitis?

Air quality affects mastitis in two ways. First, high humidity keeps bedding wet, and wet bedding supports the growth of environmental mastitis bacteria like E. coli and Klebsiella. Second, poor air quality stresses the cow, and stress suppresses the immune system, making the cow more susceptible to infection. Managing air quality is an important part of a mastitis prevention program.

How many air changes per hour does a dairy barn need?

In summer, a dairy barn needs 30 to 60 air changes per hour to remove heat and moisture. In winter, the need drops to 4 to 8 air changes per hour, just enough to remove moisture and ammonia without creating drafts. These numbers depend on the barn design, the number of cows, and the climate. Use them as a starting point and adjust based on your ammonia and humidity measurements.

Should I keep the barn warmer or better ventilated in winter?

Prioritize ventilation over warmth. Cows are more tolerant of cold than they are of poor air quality. A barn that is 40 degrees Fahrenheit with good air quality is better for cow health than a barn that is 60 degrees Fahrenheit with high ammonia and humidity. Maintain your minimum winter ventilation rate and use cow comfort measures like deep bedding to keep the cows warm.

Related Farming Guides

This section will be populated with links to related farming guides on dairy cattle health, barn design, ventilation systems, and mastitis prevention. Check back for updates.

Related Clinical & Scientific Guides

References

National Mastitis Council: https://www.nmconline.org/
USDA APHIS Dairy Cattle Health: https://www.aphis.usda.gov/livestock-poultry-disease/cattle
FAO Dairy Production and Products: https://www.fao.org/dairy-production-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.