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Request for information on a low-tech isolation room in The Gambia - reproduced with the permission of the author - responses will follow.

By Edward Nardell, MD Moderator | 05 May, 2016

Dear Dr Nardell

A London colleague, James Seddon, has recently suggested that I contact you to see if you can advise on an effective low cost room air exchange systems for isolation of our TB patients and , potentially, suspects with VHF.

I work at the MRC Unit The Gambia where I am head of our clinical services dept. We manage a wide range of medical and paediatric problems including a significant number of TB patients admitted via our out-patient department or identified through one of our many TB studies.
We have two very basic, isolation rooms in which we manage SSP TB cases. Over the last few years we are starting to see an increasing number of patients with MDRTB although the numbers are small cf other regions in s-S Africa. Additionally, with the recent large outbreak of Ebola in the adjacent subregion we are aware of the need to improve our isolation rooms for managing any suspect VHF cases in the future. We are fortunate in that we have a relatively well resourced facility with 24 hour electricity and a skilled, on-site bio-engineering dept.

I recently applied for and successfully gained additional funds (~ $150,000) to upgrade our existing facility and had hoped to convert them into two AIIR, with dedicated bathrooms, a clean ante-room for donning PPE and an exit room for disposal of waste, doffing PPE and removal of bodies if required.
However, I have been advised by a number of colleagues, especially in S Africa, that we should aim to keep the facility is simple as possible and avoid a high tech air exchange system since they frequently malfunction. Additionally I now realize that we have significantly underestimated the build costs! I am therefore interested to know if there are any alternative, low cost but effective air exchange systems that we could incorporate into a rebuild of our exiting isolation rooms.

Any suggestions or advice you have to offer will be much appreciated.

Kind regards


Dr Suzanne Anderson MRCPCH, PhD
Head of Clinical Services
MRC Unit The Gambia
Atlantic Road, Fajara
PO Box 273 Banjul
The Gambia

Tel: +220 4496188<tel:%2B220%204496188>
Cell Gambia: +220 313 3488<tel:%2B220%20313%203488>
Cell UK: +44 7817224261<tel:%2B44%207817224261>

Leading health research in West Africa to save lives and improve health across the world




Edward Nardell, MD Moderator Replied at 1:41 PM, 5 May 2016

Dear Suzanne,

I am happy to help and I am copying my CDC colleague, Paul Jensen, who will want to add his perspective. First, I would like to ask your permission to publish your question and our responses on GHD online so that others may benefit, and so that you will receive other opinions as well. As you know VHFs are droplet borne, not aerosol spread like true airborne infections. There is no doubt that aerosols from diarrhea, coughing, etc contain infectious organisms, but the belief is that full barrier and respiratory protection protects against that. I have felt that adding full airborne precautions (that is, air disinfection) cannot hurt and is a relatively small added cost for a probably small added protection, but I would do it if I could. In this case where you are preparing for both MDR TB and VHF, you would have that capability.

I agree with those who advised you that simple is better than complex from both a cost and maintenance perspective. That you have a skilled bio-engineering department suggests that any technical solution should, in theory, be possible - except for cost and availability of parts, etc. If you were thinking about trying to maintain pressure gradients between the isolation rooms and the ante/changing room and exit room, and between them and the hallway - I agree, that will be difficult to maintain and not as effective as we once thought. Even with good negative pressure isolation, with air direction designed to keep contagion in the patient room, studies show a plume of air being dragged by personnel into and out of isolation rooms. Still, you don't want rooms actively pumping contaminated air into corridors or adjacent rooms.

The fundamental elements of airborne isolation is adequate air disinfection defined as >/= 12 ACH with some effort to keep air within the room - that is, directional airflow into the room. Maintaining simple negative pressure in the room, although not as difficult as multiple pressure gradients, still requires frequent monitoring with smoke sticks, tissue paper, flow meters, or built in continuous pressure monitoring to maintain an exhaust volume that exceeds intake flow rates. Of course, for a fully mechanical system, all windows must be closed. The system I am describing need not be extremely effective if air conditioning (cooling/heating/dehumidifying) is not included. At the PIH MDR hospital in Lesotho a simple air handling unit was designed to provide 12 ACH and negative pressure only, and was purchased with an outside maintenance program. The retrofit would require ductwork and a mechanical blower system. Any good mechanical engineer can size, design, and install such a simple ventilation system. Let's see what Paul says, but I think that is probably choice #1.

Choice #2 in my view would be cheaper, effective in my view, but unconventional. We recently published data to suggest that upper room germicidal UV (GUV) with air mixing (low velocity paddle fan) added the equivalent of 24 ACH to the existing 6 ACH in a MDR hospital in South Africa. New installation guidelines in the paper are based on that study. Installing upper room GUV with air mixing in both the patient rooms, ante room, exit room, and adjacent corridors would, in my view, produce a safe environment for patients and workers. It too requires good design, good fixtures, and scrupulous checking and maintenance to be sure it is working as intended. Even good biomedical engineers generally know little or nothing about upper room GUV - but can be trained. However, unless there is also a mechanical ventilation system providing an actual 12 ACH outside air ventilation, the system that I just described would not meet the definition of a AIIR as described by WHO and the US CDC. In my opinion such as system will be less expensive, as effective (simply based on equivalent ACR) and easier to maintain. In Russia where heating in winter is required, a biological air sampling study by Volchenkov and Jensen found mechanical ventilation 9.4 times less cost effective (cost per equivalent air change) to install and operate compared to upper room GUV. Without need for heating or cooling in The Gambia, the cost difference will be less.

A problem with GUV is that the expertise to plan and install and maintain a system is hard to come by at the moment. We hope to change that, but the model of sustainable GUV implementation that we are developing is not yet commercially available. In our view you can only use fixtures that have been fully characterized in terms of UV output in all directions (gonioradiometry) or at least total UV output (integrating sphere). At the moment these fixtures are available (as far as we know) from only two US manufacturers, both of whom sell overseas. At least 2.7 m ceiling height is required to be able to place fixtures with the bottom 2.1 m from the ground. Simple low-velocity ceiling fans are required. Windows need not be closed since natural ventilation and GUV equivalent ventilation should be additive, but that depends on the situation - air not yet disinfected could blow out to high risk corridors, waiting areas, etc.

Choice #3 would be a combination of mechanical ventilation and GUV, but that requires expertise and maintenance of two systems.

Let's see what Paul has to say...


Edward Nardell, MD Moderator Replied at 1:44 PM, 5 May 2016

Dear Ed

Dear Ed,

Many thanks for responding so quickly and informatively to my query - it is very much appreciated. We'd be very interested to explore the options you have suggested, and be innovative where good alternatives exist.

We are also considering the possibility of doing a new build rather than a refurbishment of existing facilities, which might make it easier to get the design right. We have a tight schedule to develop options with a firm of architects in the UK as there is a finite time within which to develop, finalise plans and spend the money. However, it's obviously important to get it right.

I'd be very happy for you to share this query with colleagues on GHD ( by the way what is this?) and also with Paul Jensen who, by the way, does not appear to be copied in below.

Can you just clarify option 2 bit more. You state: ..'however, unless there is also a mechanical ventilation system providing an actual 12 ACH outside air ventilation, the system that I just described would not meet the definition of a AIIR as described by WHO and the US CDC. In my opinion such as system will be less expensive, as effective (simply based on equivalent ACR) and easier to maintain.....

So I'm a bit confused by these two statements - does this mean we need some sort of mechanical ventilation system with sealed windows, ductwork etc and without which it will not work?

It may be worth saying that out biggest problems here are dust from the Sahara during the long, coolish, dry season and termites! The latter destroy nearly everything and they are slowly working their way through our ward buildings while we desperately try to replace structures to stop the building collapsing!

Thanks again for your suggestions and look forward to discussing this further with you.

Kind regards


Edward Nardell, MD Moderator Replied at 1:46 PM, 5 May 2016

Dear Suzanne,

Paul is now copied and can catch up, although he may have limited availability at the moment.

Mechanical ventilation systems for isolation require closed windows in order to control pressure differences and direction of airflow. Mixed mode ventilation, mechanical and natural, can be used for general ventilation. With such major termite problems I would think that metal and masonry construction would have great advantages over wood. Mechanical ventilation usually benefits greatly from the opportunity to construct new with ducts, etc. Except for adequate ceiling height, upper room GUV does not benefit as much from new construction - a great renovation solution.

Most architects do not know much about airborne infection control and even less about GUV, so they may advise against it. My colleagues at the MASS Design group focus on developing country designs and have had award-winning hospitals in Rwanda, Haiti, and Liberia, among other places. They understand airborne infection as well as VHF.

GHD, Global Health Delivery, On Line (GHDonline.org) is a monitored blog that deals with the implementation of a variety of global health interventions, including TB transmission control. Paul and I are two of the moderators. I will post your question and my response.



Edward Nardell, MD Moderator Replied at 1:47 PM, 5 May 2016

Dear Ed

Just following up on our email exchange below and apologies for the delay in getting back to you.
We are just at the planning stage of this process and keen to get it right and an innovative but effective approach is appealing. We are currently looking at both possibilities of either renovating the existing two isolation rooms on our in-patient facility or completing a new build, adjacent to the ward block, probably with 4 rooms plus ante- and exit rooms. I've just had a look at the MASS Design group website and they have done some very beautiful work – especially the hospital in Rwanda. It's quite inspiring. However, our project is very small and funds limited so not sure how imaginative we can be, alas!
I would much appreciate it if you could send us some more information on the simple air handling unit installed at the PIH facility in Lesotho. I've had a look on the web but could not find any specific details on it. Additionally further info on the suppliers and costs of upper room GUV would also be much appreciated.

I've cc'd above Susan Simon, who is head of projects at the MRC head office, UK. She is currently reviewing options with UK architects so suggestions for air handling options at this stage would be really helpful.

Thanks again and kind regards


Edward Nardell, MD Moderator Replied at 1:53 PM, 5 May 2016

Ed Nardell <>
1:34 PM (13 minutes ago)

to Suzanne, Paul
Hi Suzanne,

Sorry for the gaps - emails tend to get buried. I am actually modifying this over what I sent you by private email because I did not address all of your concerns.

First, I had mentioned a simple ventilation system like that used and maintained at the PIH MDR treatment hospital in Lesotho. Unfortunately, Sidney Parsons, the engineer, has passed away and I know of no other way of getting the details of that system. Any good HVAC engineer can design a simple ventilation system - it is maintaining a complex system with negative pressure that is the challenge. The dust problem you mention will be a challenge for any system - mechanical ventilation or upper room GUV.

That said, I would still urge you to consider constructing an isolation room based primarily on well-designed, installed, and maintained germicidal UV (GUV) air disinfection, both in the room and in adjacent corridors, with good air mixing. As you have been advised, this will be less expensive and easier to maintain than a high volume, differential pressure, conventional approach to airborne isolation. However, these rooms will require ventilation for comfort, presumably without heating or cooling. At PIH in Haiti we long ago constructed isolation rooms with upper room UVGI combined with exhaust fans. The purpose of the exhaust fans was primarily to assure some air turnover in the room for comfort - not to capture airborne particles from throughout the room - which they do not do well. In addition, depending on the intake flow permitted, negative pressure may be achieved as an added benefit - but not the main purpose because upper room GUV with air mixing is handling air disinfection within the room. Fully open windows in an isolation room, obviously, provides no control of air change rate or direction.

With detailed schematics we can help lay out the GUV fixtures size and number. I understand that this is new construction. Ceiling fans are common. Paul, or your local engineer, can help size an appropriate exhaust fan. It is key that exhaust fans be effective but not too loud or they may be turned off. Maintenance of UV fixtures, ceiling fans, and exhaust fans is critical and usually cannot be left to hospital maintenance alone.

Are there any concept drawings to share.


Edward Krisiunas Replied at 8:24 PM, 5 May 2016

Good evening Dr. Nardell.....thanks for the info that you share
regularly...and Hello Paul!!!

Where is the facility in Liberia that you mention? I will be traveling
there in July / August for a UN project and would be interested in seeing
the facility ( as a former Med Tech with a +PPD from years ago at St.
Francis Hospital in Hartford, Connecticut)..

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