|
 |
|
How to set up an
emergency isolation room inside a home or apartment for a
suspected infected occupant.
Copyright (C) 2021
Robert Bean, ASHRAE Fellow & Distinguished Lecturer,
Free use is granted when credited.
See also:
Simplified and Idealized
Illustration of a Portable Fan/Filter (CR) Box in a
Classroom
Revisions:
2022.01.24 added studio apartment example.
This is a triage approach and by no means implied to
substitute the combined advice from a professional engineer
and physician with experience in negative pressure rooms.
There are many factors to consider in selecting the size of
fans, filters and humidifiers. Consult a professional for
advice.
When occupying a home with
persons quarantined (healthy people living with suspected
infected person(s)) wear proper personal protective
equipment. I know that might be difficult for some, but it
is only for the prescribed time and that is short relative
to a death or a lifetime of challenges (see resources at
bottom of this page).
Note: due to the urgency of this
bulletin, there may be spelling and grammatical errors...if
butchering the English language drives you crazy to the
extent that you won't read the advice - all I can say is -
good luck. |
|
|
|
 |
|
Figure 1. Home-based isolation bedroom with
attached bathroom. The objective when a bathroom exhaust fan
is available - is to keep the bedroom under negative
pressure relative to rest of the home. This is done by
sealing up the bedroom from the rest of the home as noted,
and keeping the bathroom exhaust fan on. Introduce outdoor
air with an open window to maintain less than 800 parts per
million (ppm) of carbon dioxide (CO2). Remove airborne
particles with a minimum MERV 13 filter/fan assembly (see
images below) and humidify room air with a portable unit
fitted with ultraviolet light (UV-C disinfection). Use an
electric space heater to maintain best acceptable thermal
conditions during cold periods. |
|
|
|
 |
|
Figure 2. Home-based isolation bedroom with
attached bathroom. The objective when a bathroom exhaust fan
is NOT installed, and a window mounted fan is not possible;
keep the bedroom under negative pressure relative to rest of
the home. This is done by sealing up the bedroom from the
rest of the home as noted, and installing a box fan between
the bedroom and bathroom. Ideally the doorway opening should
be creatively reduced to the size of the fan only but making
it flexible (think curtain) for the quarantined person to
use the washroom. This will aid in pressurizing the air in
bathroom to force bedroom air out the bathroom window.
Keep the box fan on. Introduce outdoor air with an open
bedroom window to maintain less than 800 parts per million (ppm)
of carbon dioxide (CO2). Remove airborne particles
with a minimum MERV 13 filter/fan assembly (see images
below) and humidify room air with a portable unit fitted
with ultraviolet light (UV-C disinfection). Use an electric
space heater to maintain best acceptable thermal conditions
during cold periods. |
|
|
|
 |
|
Figure 3. Home-based isolation bedroom with
attached bathroom. The objective when a bathroom exhaust fan
is NOT installed, and a window mounted fan is not possible
and fans are not readily available (this approach relies
on the wind and is an emergency approach only until a fan
can be installed); keep the bedroom under negative
pressure relative to rest of the home. This is done by
sealing up the bedroom from the rest of the home as noted,
and opening up the bedroom and bathroom windows. Ideally the
bedroom window should open into the wind (think sail) and
bathroom window against the wind (think blowing across the
top of an open bottle). When the wind is blowing it is
possible (but not reliable) to use this set up to draw
outdoor air into the bedroom and have it pulled out of the
bathroom window (have your kids study Bernoulli).
Adjust the bedroom window opening to maintain less than 800
parts per million (ppm) of carbon dioxide (CO2).
Remove airborne particles with a minimum MERV 13 filter/fan
assembly (see images below) and humidify room air with a
portable unit fitted with ultraviolet light (UV-C
disinfection). Use an electric space heater to maintain best
acceptable thermal conditions during cold periods. |
|
|
|
 |
|
Figure 4. Home-based isolation bedroom with
attached bathroom. The objective when a bathroom exhaust fan
is NOT installed but it is possible to install a window
mounted exhaust fan; keep the bedroom under negative
pressure relative to rest of the home. This is done by
sealing up the bedroom from the rest of the home as noted,
and installing a window mounted exhaust fan in the bathroom.
Creatively reduce the window opening to just the size of the
fan (think cardboard). Keep the exhaust fan on. Introduce
outdoor air with an open window to maintain less than 800
parts per million (ppm) of carbon dioxide (CO2).
Remove airborne particles with a minimum MERV 13 filter/fan
assembly (see images below) and humidify room air with a
portable unit fitted with ultraviolet light (UV-C
disinfection). Use an electric space heater to maintain best
acceptable thermal conditions during cold periods. |
|
|
|
 |
|
Figure 5. Home-based isolation bedroom
WITHOUT attached bathroom. The objective when a bathroom
with exhaust fan is NOT available is to keep the bedroom
under negative pressure relative to rest of the home. This
is done by installing a window mounted exhaust fan to pull
air out of the bedroom and encouraging
uncontaminated/treated air from the home to travel under the
door into the bedroom. Creatively reduce the bedroom window
opening to just the size of the fan (think cardboard). Keep
the exhaust fan on. NOTE: this approach requires those home
occupants not in quarantine - to be healthy verified by
testing and executing low risks in day to day activities.
The replacement air must be of good quality. Adjust windows
in home to maintain less than 800 parts per million (ppm) of
carbon dioxide (CO2) Remove airborne particles with a
minimum MERV 13 filter/fan assembly (see images below) and
humidify room air with a portable unit fitted with
ultraviolet light (UV-C disinfection). Use an electric space
heater to maintain best acceptable thermal conditions during
cold periods.
WARNING: This
approach (and others noted) carries a potentially high risk
of introducing carbon monoxide (CO) into the home from
natural draft (unsealed) appliances and fixtures such as
furnaces, boilers, water heaters, stoves, fireplaces, and
pollutants from attached garages etc. At no time should the
exhaust fan operate unless the windows in the home are
adjusted open to prevent back drafting. If this describes
your home and you have no other alternative for an isolation
room, then at the very least purchase an aviation-grade
carbon monoxide sensor and alarm similar to those made by CO
Experts. Install safety alarm in a common hallway serving
the occupied spaces. These alert at lower and much safer
values than UL/CSA products. Expect to pay a premium for
this safety device. If you do not know if you have natural
draft appliances and fixtures, consult a mechanical
contractor or engineer. Read our legal disclaimer noted at
the bottom of the page. This is not child's play - carbon
monoxide kills. If you are unclear what this means, you are
better off battling COVID than dying unnecessarily of CO
poisoning. This is a case where professional advice must be
sought out...you have been warned. |
|
|
|
 |
|
Figure 6. Home-based isolation bedroom
sharing a common bathroom with a non-isolated bedroom. The
objective is to keep the bedroom under negative pressure
(right side) relative to rest of the home; and be able to
make the bathroom available to the non quarantined person
(left side) (see Figure 7 below). This is done by sealing up
the isolated bedroom from the rest of the home as noted, and
exhausting with the ceiling or window mounted exhaust fan
(as shown) in the bathroom. If necessary, creatively reduce
the window opening to just the size of the fan (think
cardboard). Keep the exhaust fan on. Introduce outdoor air
into the isolated room with an open window to maintain less
than 800 parts per million (ppm) of carbon dioxide (CO2).
Remove airborne particles with a minimum MERV 13 filter/fan
assembly (see images below) and humidify room air with a
portable unit fitted with ultraviolet light (UV-C
disinfection). Use an electric space heater to maintain best
acceptable thermal conditions during cold periods. |
|
|
|
 |
|
Figure 7. As above in Figure 6 but shown set
up for bathroom access to non quarantined person. The
objective is to keep the air from the isolated bedroom from
contaminating the rest of the home/apartment/condo. The non
quarantined person should coordinate with the isolated
person so that the bathroom is used for as short as period
of time as possible. To change over, the quarantined person
should vacate the bathroom, close the bathroom door and
remain in bed with the bedroom portable filter on. The
bathroom exhaust fan should be on all the time. After a few
minutes of purging the bathroom air, the non-quarantined
person should don personal protective equipment (PPE) and
enter the bathroom to disinfect. Use N95 grade mask if
available and face shield...search online for best
practices) and seal the bottom of the isolated room door
with a towel. If it is a pocket door tape the perimeter gaps
with masking tape. Continue to let outdoor air flow into the
bathroom from the open window to maintain less than 800
parts per million (ppm) of carbon dioxide (CO2).
Remove airborne particles with a minimum MERV 13 filter/fan
assembly (see images below) and humidify room air with a
portable unit fitted with ultraviolet light (UV-C
disinfection). Use an electric space heater to maintain best
acceptable thermal conditions during cold periods.
|
|
|
 |
|
Figure 7a. Studio apartment based isolation
strategy for those on a tight budget. The objective is to
maintain a steady supply of outdoor air mixed with filtered
air flowing through the apartment into the bathroom and out
the bathroom exhaust fan. If you can not afford a CO2 meter
to regulate outdoor air flow, then control the window
opening so that the baseboard heater doesn't freeze. For
very cold climates you may have to cycle the opening times.
If the stove and range are electric run the bathroom fan
continuously. If you have a gas range increase the window
opening during times of use.
Leave the bathroom door open except for times
requiring privacy. Block the entry door threshold with a
towel. A single MERV13/Filtrete 1900 strapped to the
backside of a box fan is better than no filtration (see Fig
8, item 1) If you can afford it, build a four-panel
filter/fan assembly known as #corsirosenthalbox (Fig. 8,
item 5).
Occupants must be masked with ~N95's (see
Fig. 11), work out schedules for masking breaks, allow 20 to
30 min between bathroom rotations to allow the exhaust fan
to fully replace bathroom air with air from the living
space.
Work out schedules for eating...uninfected
and infected person should not be unmasked at the same
time...the greater the time between eating rotations the
better. Objective is for uninfected person to NOT breathe
any residual contaminated air left behind by the infected
person while unmasked.
Infected person should be positioned closest
to the bathroom exhaust and the uninfected person closest to
the open window. |
|
|
|
 |
|
Figure 8. Examples from the authors inventory
of DIY filter/fan assemblies, instruments and humidifiers.
All the components are available online.
1. Two stage filter/fan assembly (1" MERV 8
then a 1" MERV 13 then the fan). Strap filters to the inlet
of the fan with zip ties. Air should enter the MERV 8 first
then the MERV 13 then the fan. Manufacturers will mark the
proper airflow direction on the filters...do not reverse.
This set up will do most bedrooms with the lower cost MERV 8
pre-filter extending the life of the more expensive MERV 13
filter.
2. One stage filter/fan (4" MERV 13 then the fan). Strap
filter to the inlet of the fan with zip ties. Air should
first enter the MERV 13 then the fan. This set up will do
most bedrooms. Without the MERV 8 pre-filter use a 2" or 4"
MERV 13 filter.
3. CO EXPERTS Low Level Sensor and Alarm. Available through
http://coexperts.ca/
4. ARANET4 CO2 sensor. Available through
https://naltic.com/aranet4-co2.html
5. One stage - 4 sided filter/fan (MERV 13). Assemble the
four filters in a box shape with construction tape using the
shipping box from the fan on the bottom. Place the box fan
on top of the filter assembly and seal to filters with
construction tape. Airflow is through the filters then out
the top.
6. Honeywell UV-C humidifier. Will do about
150 sf bedroom. This is an occupant controlled
device...adjust fan flow so that the room moisture remains
below condensation point on windows.
Last words: I spent nearly 40 years designing
indoor climates...this is triage...are there better ways of
doing this? Yes. There are more sophisticated devices and
instruments and controls but for these consult a
professional...what I have provided here will serve in a
pinch if someone must be isolated.
Stay safe and please for the sake of our our
already stressed out healthcare workers - do your part to
keep others COVID free.
My three rules to stay safe:
1. There is no definitive safe social
distance nor time- the virus and the particles it travels
in/on does not have an onboard navigational system or a
clock! The air is a conveyor belt...where it goes - so goes
the virus. Physics wins every time. Just stay as far away
from others as you can!
2. Wear proper masks properly in the presence of any unknown
risks including friends and family. See your health
authorities on masking protocols. Don't be delusional and
think any fabric will do. Fabrics used for filters is a
engineering science. Trust the science not the glossy sales
brochure.
3. Personal and building hygiene is good but it is not a
substitute for air hygiene which comes from ventilation and
filtration. See your heath authorities for personal and
building hygiene and ASHRAE for air quality strategies. See
https://www.ashrae.org/technical-resources/residentialnew
Please sign the petition and encourage others to do so at
https://www.covidisairborne.org/
Resources:
https://tinyurl.com/FAQ-aerosols
https://tinyurl.com/y36zolmz
https://tinyurl.com/y5zoannt
|
|
Additional Content: Treating the air in high use spaces such
as home offices and bedrooms. |
|
 |
|
Figure 9. Authors home office...note the
portable fan/filter on filing cabinet and humidifier on
floor. |
|
|
|
 |
|
Figure 10. Authors 4 sided 1" MERV 13
filter/box fan assembly suitable for about a 200 sf room |
|
|
|
 |
|
Figure 10. Master bedroom...note the portable
fan/filter on dresser. This is a HEPA/carbon filter. Not
shown is the same portable UVC Humidifier as used above. |
|
|
|
 |
|
Figure 11. Authors sample of masks
(elastomeric, N95 et al), rapid antigen test kits,
environmental sensor (CO2, RH & Air Temperature), finger
type: oxygen saturation and pulse meter |
|
|
|
 |
|
Figure 12. Personal story...I know from
experience what it's like to almost die from respiratory
failure. Short strokes - you and yours want to take every
reasonable step to avoid becoming infected. Defend your
personal air space, wear proper masks properly, get
vaccinated with boosters, ventilate and filter the air in
the spaces you occupy. If you or yours still become infected
the resources you need at home are mostly affordable and its
relatively easy to isolate those infected from those
uninfected. |
|
|
