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Climate change

HVAC systems do more than just adjust the ambient air temperature. They’re also crucial for controlling odors, humidity and the spread of pathogens.

Climate change
A reception area provides an ample supply of fresh air.

When clients walk in the door, you want them to sense that the hospital environment is of the same quality as the medicine you practice. Do they notice odors and noise, or is the clinic clean, bright and fresh? How your hospital performs and how it is perceived by clients and team members is influenced in no small part by the quality of the indoor environment. Your building’s heating, ventilation and air conditioning (HVAC) system plays a major role. A good system not only provides comfort but also mitigates foul smells and keeps loud dog barking from resonating into every corner.

Comfort Is Subjective

A word about comfort: While most people prefer a certain temperature and humidity range, the level varies widely from person to person. We all know someone who is always cold or always hot. Put three people in a room and you’ll get three opinions about comfort.

The fact is, comfort is subjective. It’s not possible to make everyone comfortable all the time. While HVAC systems featuring individual room controls can be installed, they are quite expensive and usually are well out of the budget allowance of a private-practice hospital. Achieving a middle range so that most people are comfortable almost all the time is the more affordable goal.

Beyond comfort considerations, veterinary hospitals present unusual challenges to HVAC designers. You want experienced mechanical engineers involved. Ultimately, the engineer is the one who must select properly sized equipment and assemble it into an integrated, whole-building solution.

Cost Versus Expectations

Just as you need a program document as the basis for a building design — how big, what kind of rooms and what size budget? — the mechanical systems need to be chosen before work can begin.

Exam rooms are difficult to design. They are small spaces when you consider how many people use them and how often. Exam rooms are busy during intake and discharge. Sometimes they’re occupied by two people and a pet for five minutes and other times by a family, the doctor, a veterinary technician and a panting Great Dane for a half-hour with the door closed. Other times, the rooms are lightly used or empty for hours.

Systems that cannot modulate based on occupancy load often do not support ideal conditions. How much are you willing or able to spend on a high-end system? Some perform exceptionally well, but there is a point of diminishing returns. Meeting with your design team and especially the mechanical engineer is an essential first step. To help you with that conversation, let’s go over the issues you should focus on.

Humidity and Temperature

Condensation, mold and comfort are a function of humidity. In general, the damper a space is, the less comfortable it is. The fact that dry heat is better than humid heat holds true for cooling, too. One big reason an air-conditioned space is more comfortable is that it is drier. A damp chill makes you feel clammy. Anyone living in a high-humidity climate knows this all too well.

Fighting ambient outdoor humidity is an important function of an HVAC system, and most do it quite well. Unfortunately, veterinary hospitals produce a lot of indoor humidity, too. Washed floors, wet kennels and steam from autoclaves, bathing and grooming contribute to higher than desired dampness. Ideally, you want to maintain a 50% indoor relative humidity to support comfort, reduce condensation and control the growth of mold and pathogens. Many commercial systems can measure and control humidity independently of the temperature, so your mechanical engineer needs to determine all the sources of moisture and design for them.

Limit Pathogens

While humidity control is an important feature for preventing the spread of pathogens, more can be done. By code, HVAC systems must be reasonably energy-efficient, so that means all the air can’t just be exhausted and replaced by fresh air. Some of the energy used to condition air must be recaptured by recycling. Outside air is mixed, but most is reused.

Outside air is generally used only for ventilation and to maintain a good balance of oxygen and carbon dioxide. If we recycled all the indoor air, carbon dioxide levels would slowly rise and oxygen levels fall. To prevent unacceptable levels, recycled air is mixed with small amounts of outside air, typically 10% to 30%. This works well to minimize energy usage but also means reused air is efficiently spread throughout the hospital.

Now, what if that air contains pathogens? How do we keep one patient from infecting all? Aerosolized droplets and viruses travel on air currents and have no problem hitching a ride through the HVAC system.

Rest assured, a few things can be done:

  • Segment the building to segregate which spaces share air.
  • Filter the air.
  • Sanitize the airstream using devices such as a UV-C (ultraviolet germicidal irradiation).
  • Block recycled air from entering from high-risk areas.

Limit Odors

Veterinary hospitals play host to many odor sources: animal waste, electrocauterization, laser surgery, dentals, built-up residue in runs and wards, and even employee food. (I’m looking at you, you reheated fish lover!) How can your clinic be kept from smelling like the hospitals of old?

Certainly, the single best control method is to clean the odor source as soon as you can — no source, no odor. To prevent contamination of client areas, the building can be segmented, or zoned. I’m talking about three major zones: the front client area, the center clinical areas, and the rear housing and utility areas.

If the front zone is designed with positive pressure relative to other areas, the air will move from the front to back. Any odors created in treatment areas should not drift to the lobby. The central zone would be negative relative to the front zone. The intent is to keep odors in the source room or move them toward the rear until cleaning occurs.

The Noise Problem

One issue with air supply systems is that they can transmit noise. They are frequently the culprit when a small barker in a treatment room is making patients nervous in the lobby or why a conversation in one exam room can be heard in another.

Air ducts are commonly constructed of sheet metal. These long tubes of reflective surfaces easily carry sound a long way. If a duct supplying air to treatment areas extends to the lobby, you and your patients will hear every bark and yip despite the nice sound-barrier walls you installed. Again, zoning is a strategy to mitigate sound leaks, so the proper routing of ducts and the strategic use of acoustical linings and flex ducts will go a long way in eliminating the problem.

Don’t Forget Maintenance

It’s no secret that veterinary hospitals produce considerable amounts of fur and dander that constantly clog filters, grilles and diffusers. Thought must be given to how and who will maintain the HVAC system. Only the largest of hospitals can afford full-time facility maintenance (not cleaning) people.

If you do the maintenance yourself, ease of access and simple filter changes are best. However, I recommend a service contract that calls for frequent filter changes — usually every three months — and inspection of the surgery HEPA filter at least twice a year.

Other Considerations

Here are some rooms that need special attention when an HVAC system is installed.

  • Exam: When clients are made uncomfortable for an extended period, they are not in a good frame of mind for listening, understanding, making decisions and accepting recommendations. Make exam rooms as comfortable as your budget permits. Client perception of your entire business can be made or broken in this room.
  • Surgery: A sterile operating field needs to be maintained. I do this by introducing ​HEPA-filtered air in a downward flow directly over the operating table. Laminar flow (minimal turbulence) is appoximated using low wall return grilles. In this way, only filtered air touches the surgical field. There’s also a temperature issue — the surgeons themselves. Being gowned for hours under bright lights can become stifling even with direct airflow. Ideally, the air temperature should be adjustable independent of other rooms in the zone. One way is to use a supplementary mini split air conditioner as long as it does not blow across the sterile field.
  • ICU and treatment: They might be separate rooms or a common space. However configured, they are the heart of the clinical area. The strategic use of exhaust fans is key, much like a hood over a kitchen stove. At least one exhaust fan near a treatment table or cage bank is typical.
  • Isolation: This high-risk room should not return any air to the HVAC system. All the air should be exhausted when the room is occupied.
  • Pack and prep: Pack sterilization usually happens with a steam autoclave and is a source of humidity. Consider using a ceiling exhaust fan that can be switched on when necessary. I suggest installing a timer switch so that the fan isn’t left on inadvertently.
  • Bathing and grooming: Major sources of humidity, these services are typically performed in a separate room. The equipment type and size will depend on the frequency of use. An exhaust fan might be enough, while separate heat and humidity mitigation might be needed at other hospitals.
  • Feline wards and boarding: These are major odor producers, so an exhaust fan and minimal or no air returned to the HVAC system are the norms. Some cat condos permit litter compartments to be exhausted directly.
  • Dog wards and boarding: If possible, don’t return the air to the HVAC system. Constant cleanup protocols are important here. Non-absorbing surface finishes will help, but there’s no substitute for removing the odor source as soon as possible. Another issue is humidity, especially with indoor-outdoor runs separated by flaps or guillotine doors. Consider an indoor-outdoor run as an outdoor space and strive to temper rather than fully condition the air.

Constructive Criticism columnist Paul Gladysz is the principal architect at BDA Architecture. The Albuquerque, New Mexico, firm specializes in the planning, design and construction of animal care facilities.

HVAC system

Exhaust tubes carry odors away from litter compartments in a feline ward.