Josh Theodore

When did work on the isolation unit start? How did the project get off the ground?

We started design meetings with the Centers for Disease Control and Prevention (CDC) and with Texas Children’s Hospital in November of last year. We had a full kickoff in December and finished tender documentation in April. We had a contractor on board from day one, so this was not a design-bid-build project. The contractor and subcontractor were all engaged since the beginning of the project. Everybody knew what to do, how to do it and what the intent was. We worked with manufacturers on what types of Air Handling Units (AHUs) to use. We ended up going with Temptrol custom units. And the AHUs all have fan arrays or fan wall technology.

Since it’s an isolation unit and not a standard healthcare facility, what special design considerations did you have to keep in mind while working on the project?

The unit specialises in infectious diseases like Ebola, MERS, SARS and avian flu, among others. The airborne respiratory diseases are the most contagious, and, in some cases, highly fatal. As for Ebola, it has gotten a lot of attention because of the high fatality rate, but it’s fluid-borne, so it’s not as easily transmitted as most people believe. But if you’re a caregiver in that environment, then you are susceptible to it. That is if you don’t go through the proper PPE (Personal Protective Equipment) donning and doffing procedures, which is why there’s much emphasis given on the gowning process – putting it on and taking it off – and making sure that everything is done appropriately.

We also used low air returns to keep particulates, viruses and bacteria from being up where we are breathing and pull as much of them down, as low as we can

Within each environment or section of the isolation unit, we needed to ensure correct air flow. If main corridors are green or cold, then moving deeper into the isolation unit should take us to rooms with negative air pressure. For example, if we go from a main corridor to the anteroom, the anteroom should be negative, and going from the anteroom to the patient room – which will be a hot zone – should mean further negative air. This is to make sure pathogens go into the negative space as the air in the room moves. We also used low air returns to keep particulates, viruses and bacteria from being up where we are breathing and pull as much of them down, as low as we can.

For Texas Children’s, the floor dynamic showed that we could provide mid-level return air where the patient bed is, so that if the patient is in the bed coughing, we could pull the contaminated air into the wall and not let it move around the room. And again, that has more to do with MERS, SARS or other types of airborne transmitted diseases rather than Ebola. With Ebola, you get hemorrhagic vomiting and diarrhoea, which means we’re basically dealing with fluids – beyond the scope of air control. We had to look at products and materials that can handle rigorous cleaning and disinfection. We also had to make sure we didn’t have seams or crevices that could harbour germs. Thus, we looked at coves, at smooth surfaces that could be easily wiped and disinfected. We also had to look at UV lighting for disinfection and full aerosolisation of a room when it’s emptied out.

What do you mean by “green or cold” and “hot zone”? 

Imagine traffic lights. We have green, yellow and red. Green is go, which means green is good. In the case of an infectious diseases area, green is cold, meaning that it’s clean. Yellow is warm, which means that the area may have fluid or contaminant. And red is hot. When we’re in a hot zone, there’s a definite possibility of microbes, virus and bacteria within the space.

I understand that ACH (air changes per hour) is another major consideration when designing facilities intended for the treatment of infectious diseases. What is the ACH rate for the unit in Texas Children’s Hospital?

We go for 99.95% HEPA filters to ensure that we get very clean return air

The minimum criteria, in the United States, for an isolation room or an infection intensive care room, which is where this would fall under, is only 12 air changes per hour, but the CDC guidelines indicate 20 ACH. This means that more air needs to move in the room, that a different design is needed for the AHUs, that most, if not all, of the air in the room must be exhausted and that HEPA filtration has to be looked into.

For this project, the rooms themselves are fully exhausted, but in the main part of the unit, we have recirculated air and HEPA filtration, which means we have a blend of systems. But we did put new air handlers on the roof to handle the BSL-3 (Biosafety Level 3) laboratory itself as well as the BSL-4 hot zone. A standard patient room has, depending on the code being used, four to six ACH. In the case of the isolation unit for Texas Children’s, we are at five times that number. In the donning/doffing and isolation rooms, the ACH rate is 15 to 20. In the BSL-3 lab, ACH is 30.

We’re really looking at more fresh air coming into the space. Also, depending on the climate that you are working in, you’ll have different levels of humidity and temperature control, so the air you’re bringing in may need to be either dehumidified or humidified. In the Arabian Peninsula, for example, it gets humid during sunrise and sunset, but is very dry in the middle of the day, so sometimes you actually have to add humidity to the air. That’s an element that you have to take into consideration.

Filtration is, of course, a must, especially if you’re returning the air. We go for 99.95% HEPA filters to ensure that we get very clean return air. That’s the main thing. But you must also remember that the more fresh air you bring into a space, the more air you’ll have to condition and treat. So, there’s energy cost to think about, which is another reason we prefer using HEPA filters. They make air reusable within the care environment, which means you can save energy, because you don’t have to exhaust conditioned air immediately.

In this project, air in a BSL-3 lab and all other red areas are exhausted. Air in non-contaminated areas, on the other hand, is returned.

Did you have an air quality consultant working with you?

We did. There were consultants on board for that. Also, because this was a renovation project in an existing hospital, even though it involved an empty floor, we had infection control and risk assessment standards. And we measured the air quality, in the construction space and immediately outside it, to make sure that contaminants – even from construction – would not affect the rest of the hospital.

Was any element incorporated into your design solely because the facility is intended for children? 

The colour schemes of the rooms are more child-friendly. The main thing, though, is the involvement of the parents. They can’t be in the same room as their highly contagious child; but, of course, we didn’t want to keep them completely away from their child. The solution was to provide a space where the parents don’t have to be fully gowned, but can still converse with their child. It’s already very intimidating for the child to be in there, as it is, with everybody in a protective suit. The children don’t have to see their parents that way.

It’s reassuring for a sick child to be able to converse with Mom and Dad and to see them looking just the way they normally do. That was part of the reason why, when we designed the isolation unit, we decided against making the whole unit meet BSL-4 criteria. We limited that to the patient rooms. As for the rest of the unit, while it is kept very clean and has proper air flow and protocol in place, it has spaces where you can just be in general scrubs or regular clothing.