The studies are from the 70s and 80s. The two main ones that speak to the lack of aerosol transmission of feline respiratory pathogens are:

1. Gaskell RM, Povey RC. Transmission of feline viral rhinotracheitis. 1982
2. Wardley RC, Povey RC. Aerosol transmission of feline calciciviruses. An assessment of its epidemiological importance. 1977

Here are some relevant FAQs from our website.

1. Managing feline respiratory disease in foster
2. How can I decrease the spread of feline URI within my shelter?

Dr. Hurley got to meet one of the authors of those early papers, Roz Gaskell, who did a lot of foundational work on our understanding of feline respiratory disease transmission. Some of this work was in her PhD thesis, in addition to the studies referenced above. In her studies, Dr. Gaskell placed cats in open wire cages at least ~ 6 feet apart and made sure caretakers handled healthy/susceptible cats before the sick cats. There was no transmission even though they shared the same air space in a fairly small room. However, as soon as she reversed the order and allowed caregivers to handle the sick cats before the healthy/susceptible cats, there was transmission, showing the importance of fomite transmission for this disease. This is yet another reason why double compartment housing is so important, as it allows cleaning and basic care to take place without having to closely handle animals.

Assuming this question is focused on cats, remember that none of these diseases is transmitted through the air, so it probably isn’t necessary to specifically address airborne pathogens in cat housing spaces. However, there are ways that air purifiers can have value in these areas:

PCO ionizers show some value in disinfection of surfaces and so may help reduce fomite/environmental contamination and the associated risks of ongoing transmission.

Removing particles from the air can support respiratory tract health overall and make it easier for cats to fend off or recover from URI.

Optimizing AQ inside all areas within the shelter will provide health benefits for all animals and people, with particular value for those who are more at risk from diseases due to age or immune system compromise.

Even where airborne spread of pathogens is less of a risk (e.g. among cats) good AQ helps to support general respiratory tract health, which may help limit how many animals get sick or how severely sick they become.

Finally, don’t forget how important people are to the day to day work you are trying to do for the animals, and helping to reduce respiratory disease (infectious or not) can help ensure you have the staffing and volunteer levels you need to do your best work.

Thinking about all canine respiratory disease pathogens broadly (pneumovirus management isn’t unique), anything moving about in the air is going to spread out (diffuse or become less concentrated) as distance from the source increases. If you don’t have a physically separate iso space but can create a makeshift iso space that’s functionally separate from gen pop by creating as much distance as possible (ideally at least 25ft) between sick animals & healthy animals, that can help. I hear you that you don’t have input over some facets of operations at your shelter but if you have some say over other things that are risk factors for canine infectious resp disease – crowding, stress levels, constant barking that worsens respiratory airway health- working on those will help too.

A full outbreak response with new intakes slowed or temporarily halted in order to establish a clean break may be necessary to fully disrupt ongoing transmission within your population. See the Outbreak Management section of our Canine Influenza info sheet.

As noted in the previous question, distance can very much help reduce airborne disease transmission. However, getting ahead of respiratory disease and staying ahead is likely not possible without addressing the primary problems of crowding and capacity for care.

We don’t have specific companies to recommend, but there are a few approaches you could take.

An architectural firm that specializes in animal facilities can offer insights on many aspects, including HVAC systems. You could engage such a firm to advise the specific companies you hire to do the work. In this case you just need to make sure the company you hire for your build project is willing to work with the advising firm.

If this is not possible, some fundamentals you can share with the company you are hire are that:

• Air conditioning and ventilation must support comfort and air quality at the level of people and at the level of animals within their housing units. How will the system work within the rooms and the housing units?
• Isolation wards are the only area that warrant a separate exhaust system and the ward should be designed to be a negative pressure area relative to other areas to help insure that air moves into that space and not out of it. If air is getting recirculated in your HVAC system, air from these rooms would not get recirculated into the overall system and should be separately exhausted.
• If you will have a surgery clinic onsite, the surgery suite should be be positively pressurized so that air passively is pushed out of this space rather than into it. Consider whether a higher rated filter for the air entering the surgery suite is indicated given the overall design of the HVAC system.
• Ask about the filters that will be used on your HVAC system. HVAC systems that can work with MERV 13 filters will allow for better air quality within your shelter and reduce more of the smaller particulates from entering the facility – including pollens and smoke should you be in an area where these are problematic.
• Ask about maintenance and make sure your team has the ability and resources to keep up with needs.
• Do you want or need other tools to improve indoor air quality? Ensure units selected are safe and effective and understand maintenance needs and costs.
  • Are you interested in in-duct “disinfection” systems like UV purifiers?
  • Other air purifiers can be used without integration into the HVAC system if desired – such as Photocalytic Oxidizer (PCO) units and in-room air filter units – generally HEPA type filters. Are there areas where ventilation or overall comfort will be difficult to maintain by the overall HVAC and additional investment is warranted?
• Understand the impact of open windows and doors on your HVAC system’s air flow – especially through animal housing spaces.
• Finally, make sure that you can maintain whatever system you decide to go with– this often means finding or working with companies with local affiliations to ensure maintenance and repair can be done in a cost-effective and timely manner.

The devices that emit light into a space from a device like a wand are usually called “UV sanitizers” which are distinct from UV air purifiers. We didn’t specifically review the effectiveness of sanitizers, so I can’t say for sure, but the same principles Dr. Wagner noted would theoretically apply. For safety and efficacy considerations know what wavelength is emitted, if ozone emissions are a risk, and investigate other potential safety issues. Shining the sanitizer on a surface may be helpful (if there was enough time to inactivate a pathogen) but it probably wouldn’t do much for pathogens in the air. All in all, without good evidence, it doesn’t seem like a reliable way to decontaminate surfaces or personnel clothing.

Instead, for practical reasons, we would recommend implementation of good standard practices for preventing fomite spread:

1. Minimize animal handling during routine daily care.
2. Each animal housing room should have its own cleaning tools and they should not be shared across rooms.
3. Cover clothing or chang clothing that is used by staff during cleaning time.
4. Practice handwashing or use of hand sanitizers between animal rooms where possible.

A photocatalytic oxidation purification device (like the Puraclenz) that distributes ions consistantly across the entire area housing animals, including the air and surfaces, may be a better tool to employ in animal housing spaces to reduce the overall load of pathogens rather than trying to use a wand sanitizer.

However, no purifier or UV wand will penetrate into hair and poop and litter particles that get on clothing during cleaning, so staff should change at least tops before moving on the next activity.

There are a number of variables to consider to make that decision. First, look up whether your specific air purifier has been certified to meet low ozone emission standards. If it has not, the health risks from ozone suggest you probably should not.

Second, does the manufacturer have evidence or certifications that the ionizer is effective? What area is the ionizer rated for and how does that compare to the space you are using it in?

Last but not least, what are your goals (i.e. target particles) for your purifier? If you are primarily trying to eliminate dust or larger particles, a good filter (check i’s rating) should be sufficient. If you are also trying to target microbes on particles in the air, and you have investigated the questions about efficacy and safety, then it may add some value to use the ionizer.

Use of spot-cleaning where appropriate will have the greatest impact to help limit the use of water and cleaning products both because less of each will be used and also because spot cleaning does not typically involve spraying large volumes of cleaning agents or water e.g. via hose sprayers. See our Spot Cleaning Dog Kennels info sheet. (/library/resources/spot-cleaning-dog-kennels)

Temporarily increase air movement in the room with floor fans, fans in ceiling areas, etc. during cleaning time periods as this should quicken the drying process. (Reminder – do not place fans such that animals are impacted and experience a draft). Make sure your HVAC system is operating properly so that humid air or air containing lots of aerosolized cleaning products will be replaced by fresh air. Remove as much water in the cleaning process as possible – all wet floors should be squeegeed to a drain. This will also support faster drying of surfaces, which is important as animals should not be moved back into wet housing units.

Placement and use of exhaust fans in dog kennel rooms can sometimes be used to remove air and improve air quality during cleaning time.

Use of pressure washers is likely to create aerosolized water/cleaning products as the high speed of moving liquids will allow more particles to be sheared away from the liquid stream and become suspended in the air. We highly recommend that solids be picked up prior to the cleaning process. If solid waste is not cleaned prior to spraying it is possible to aerosolize the waste – including pathogens like parvo that normally wouldn’t be spread through the air. For lower pressure systems there isn’t much evidence of a difference in aerosol generation for foaming vs droplet spraying systems.

Having temperature, humidity and CO2 monitors in the space will allow you to compare any point in time to the target zones suggested for comfort of people and animals. It is expected that during cleaning time the humidity will rise above the target zone desired – however the overall goal should be that it returns fairly quickly to normal. If there are long periods of the day – hours, that the kennels are wet or the kennel room is very humid – investigate your HVAC system and check to see that it is working properly or if there may be additional tools available to improve air quality. Dehumidification may be warranted if those housing spaces are constantly wet. Where having those monitors isn’t possible just pay attention to how it feels to be in a space – if it feels too hot, too humid, or uncomfortable in another way, that is also useful information that you can use to make decisions.

To some extent the answer to this depends on why humidity is a challenge. Is it an indoor-outdoor dog ward, and the outdoor environment is very humid? Are staff spraying a lot of water during cleaning? Another reason altogether?

If your shelter has not embraced daily spot cleaning (/library/resources/spot-cleaning-dog-kennels) this can make a big difference.

If the population is relatively healthy, using fans to push air into and out of the room can promote drying of the environment, but make sure you aren’t just moving stale, contaminated air around a room-this may contribute to canine respiratory disease.

Placement and use of exhaust fans during cleaning time may be something to explore for a room where the HVAC system is working properly but you’re still having issues with slow drying or high humidity especially after cleaning.

Finally, it is possible that a dehumidifier (associated with the HVAC system or in the ward where humidity is a challenge) may help. This is not likely to be useful (and may be expensive to operate) if the exterior environment is the source of humidity and the ward is open to the exterior. Getting dog doors in addition to guillotine doors can help with maintaining conditioned air and save on costs over the long run.

Fans can be helpful to create air movement across a wet surface to assist in drying it. However, they may also contribute to mixing of the air and potentially spreading respiratory pathogens (dogs/people) and other airborne particles.

Sometimes we see fans used to pull air out of rooms – such as an exhaust fan that might be turned on during cleaning time to help remove air quickly. Most of the air pulled into the room will come from other entry points of the room- around doors, etc. There may be some value in getting dryer air into the kennel space.

Fans that simply create air movement do not offer cooling benefits to cats and dogs as they do for humans (air movement causes sweat on our skin to evaporate which is why they help people feel cooler) and should not be relied on for this purpose. If however they help to circulate conditioned air (air that has been heated/cooled/humidity controlled) they may help animals and people feel more comfortable . Monitor any fans in use to ensure they are not directed at housed animals, as drafts can occur, which is undesirable for housed animals.

If particulate matter in the air is higher than desired – such as during wild fires, or in urban settings that may deal with more particulate air pollution, then filtering the air can be helpful. Use of MERV 13 filters on HVAC systems (that can support them) is the easiest way to impact the air inside the shelter. If that is not possible or there is a desire to improve air quality in a single room space then portable air filters can be very useful. The box fan filter has been around for years and can be effective for removing particulates when MERV 13 filters are used. The main issue with these DIY units are that they take up a fair bit of space and the fans are generally loud and this can be disruptive and stressful to animals in a room – especially for say a cat housing room. There are many quiet portable HEPA type filter units that can be placed in rooms to help reduce particulates and those may be a better choice than the DIY box fan filter. As with all filters they need to be changed out when recommended to remain effective. This article recently published by UC Davis (February 2025) mentions these fans and when they might provide value.

First be sure you have thoroughly cleaned any surfaces that may be contributing to a persistent odor. Some cleaning products and disinfectants are better at neutralizing odors. Avoid using strong smelling products just cover up the odor. Replace any surfaces that may be difficult to clean (e.g. wood paneled shelves where cats may have recovered in traps post-surgery).

If the smell is persisting after the cats leave and you are confident in your cleaning efforts, a persistent odor may suggest there is a ventilation problem in the room. Remember you can use an inexpensive CO2 meter to measure CO2 levels as a proxy for ventilation (when there are animals in the room). Check whether an adjustment or modification to the HVAC system may improve ventilation in the room. If not, can fans be used to pass fresher air into the space (and stale air out)? If increased ventilation is not working or possible in the space, a PCO ionizer MIGHT help, as the ions emitted do break down some odor-causing gases.

We didn’t discuss this in our webinar but use of a charcoal filter in an air purifier may additionally help. Look for air purifiers that have an added charcoal filter that can be changed out. These filters do help remove odors but must be replaced pretty frequently. It may be something that would be worth trying in this room – especially if the air is making its way out of the room too. One other thought would be to put an exhaust fan in that room – either on an outside wall or a bathroom type fan that could exhaust out the roof. Turn it on when there are cats in there and off at the end of the day. It wouldn’t address the residual smell directly but would pull air out of that room and keep it from going other places if that is part of the problem.