The current pandemic of Covid-19 is spread significantly by inhaling
droplets from infected people who are within two metres or less. Outdoor
transmission is rare: most droplet transmission happens indoors where there is
little movement of the air mass.
This paper looks at ways in which this indoor transmission
may be reduced, both in the clinical setting and in public spaces.
At the time of writing (September 2020) the pandemic is
showing signs of a second wave at a time when Governments are very strongly
motivated to get the economy moving again.
Infection control demands less interaction between people, but re-opening
the economy demands more interaction.
ADM technology presents a major opportunity to help resolve
these conflicting demands.
First, the core proposal is set out for clinical settings, then
for auditoriums, and finally for places where people are moving about freely. Detailed
considerations are set out in the second section of this paper.
This is a generic document. Other documents focused on
hospitals, bus, train, auditoriums and clubs are available.
1.
Preventing transmission from Covid-19
cases in hospitals and nursing homes
People in hospitals and nursing homes who are known to be
infected with Covid-19 are breathing out and coughing out droplets containing
the virus Sars-CoV-2 (which causes the disease Covid-19) constantly and in
large amounts, especially in the first week since symptoms began. The air in
their vicinity and in their room will contain a considerable quantity of virus.
Their bed coverings and the floor within a couple of metres will also be hosting
significant amounts of virus. These clouds and
deposits of virus present a threat to anyone visiting or attending the
patient.
Patients in hospital who are on CPAP or respirators do not
cause this problem as their air is contained in a closed circuit.
Patients undergoing procedures such as medical
investigations also present a threat of infection to their attendants given
that they may be asymptomatic carriers. Masks mitigate this risk to some
extent, but the risk is still there.
This source of potential infection from asymptomatic
carriers and/or Covid-19 patients who are not on respirators or closed circuit
CPAP will be reduced significantly if the oxygen mask that they are using were
to be adapted with a tube that will withdraw their exhaled breath from the
room.
Each individual’s exhaled air tube will be connected to a
manifold, and the total air removed from all patients in a hospital or nursing
home would be passed through a unit that will apply effective sterilisation by
chemical means (e.g. sodium hypochlorite mist), physical means (e.g. ultraviolet
light or heat) , or a combination of both, before venting to the atmosphere.
Many modern hospitals have a centralised vacuum cleaning
system that might well serve as a starting point for the air extraction ducts.
Heat exchangers should be added to minimise heat loss from
the establishment in colder months.
In a refinement, the mask may be designed so that oxygen is
supplied when the patients are in the inspiratory stage of their respiratory
cycle and cut off when the patients are in the expiratory stage of their respiratory
cycle. Conversely the exhaust air duct will open with the expiratory phase of
the respiratory cycle and close when they are in the inspiratory phase of the
respiratory cycle.
This alternate flow may be produced by simple valves fitted
at the opening of the tubes in the mask, (See Fig 1), or by an electrically
driven rotating valve fixed to the air lines (design available from author).
In a further refinement, for patients with severely
compromised respiration, electrically actuated valves could be provided which
would be controlled by information from sensors sited on the patient’s chest which
would allow synchronised delivery and extraction of gases. The patient would
receive useful assistance in respiration from this arrangement.
This positive technology which will substantially remove the
virus from the hospital environment means that hospital acquired infections,
whether by other patients or by front-line staff, would be greatly reduced. It
would remove a great deal of stress from front line staff.
2.
Preventing transmission in auditoriums
Cinemas, music venues and theatres are adversely affected by
the pandemic, since their capacity is severely restricted by the need for a
safe 1 or 2 metre gap between customers. The same consideration applies to
public transport.
ADM technology can allow these places and services to return
safely to full capacity.
In places where people sit in rows of fixed seating, as in
theatres and cinemas, each seating place will be provided with a double tube,
one bringing in filtered and purified air, and one withdrawing exhaled air. The
clients will each own their personal face mask (which will be available in the
foyer) that will fit to the tube, and on breathing in they will receive
filtered air, and on breathing out their breath will be drawn away to be
sterilised (see 1. above) before it is
vented.
In a refinement of the system, the masks may be provided
with valves that open the supply tube when the user breathes in, and opens the
exhaust tube when the user breathes out.
As an addition to this system, exhaust air from the whole site
can tested for presence of Sars-Cov-2. If the virus is found in the total
exhaust, it may be made possible to sample air from specific parts of the room,
and break down the testing to smaller and smaller sections until the row is (or
rows are) identified that contains the person who is (or persons who are) the
source of the virus.
In the case of places such as a conference or a lecture
theatre, the people from that row can be called out and tested individually.
In the case of a theatre, people from the row that is
showing infection can be notified in the interval of the performance that one
of them is carrying the virus, and if individual testing is available, each
person in the row can be tested during the interval.
3.
Offices
ADM technology can be applied to office workstations in
various straightforward ways that are laid out in detail in a separate document
available on request.
4.
Public transport
Some bus companies have introduced simple ventilation to
their buses. This is better than having no ventilation, but it has drawbacks
since horizontal movement of air from a person who is putting out Sars-CpV-2
particles is known to be able to cause spread. ADM technology can be easily applied
to buses and trains. Details will be posted here soon.
5.
Dance halls, public houses, and crowded
spaces
In some situations, it is impractical to wear masks that
deliver to, and remove air from, each individual. Places like dance halls,
pubs, clubs, locations where people are required to queue, and places where
social distancing is impractical, are areas where the risk of viral
transmission is high.
In these situations, the aim should be to create vertical
air dynamics. Purified air can be introduced at a level of about 1 metre from
the floor. These would be delivered from vents fitted to the wall, by pillars
and under tables. Air would be extracted from funnels placed a little above
head height, collected, and sterilised (as in 1. above) before venting. This
arrangement will mean that exhaled droplets and aerosols are drawn upwards and
away from other people. Transmission is still possible with this arrangement,
but the degree of transmission will be significantly reduced.
In an alternative embodiment, vertical air dynamics air may
be supplied from overhead vents and removed by designed floor tiles.
Sampling of exhaust air may be carried out as described in
section 2 above, and if viral load of exhaust air passes a set threshold, the
crowd can be notified so that those who do not wish to run the risk of
infection can leave. If the viral load exceeds a higher set threshold, the
event will be terminated.
It should be noted that air quality in many clubs is already
in need of improvement regardless of the pandemic, due to sweat, body odour,
perfume, body heat, low levels of oxygen
and high levels of CO2, so the uptake of AQ management in clubs may eventually
be widespread.
Discussion
Cost
There will be a significant capital cost attached to fitting
these air management tubes, fans, filters and sampling activities, but the
costs will be recouped from increased revenue arising from higher attendance
figures. It is possible that Government may be persuaded to subsidise these
technologies in order to suppress the pandemic.
Apparatus will not have to be scrapped when the Covid-19 pandemic
is over. Pandemics are arising more and more frequently as shown in this table:
Table 1
HIV/AIDS ~1940
Ebola 1976
Sars 2002
Mers 2012
Covid-19 2019
It can be seen that the interval between emergence of new
infections is decreasing with time, and we can safely infer that new pandemics
will occur from time to time, and therefore the demand for air dynamics management
equipment will be sustained and increased.
Other
measures
Air Dynamics Management must be seen as one component of a systematic
response rather than a magic bullet to stop the pandemic. Hand hygiene, social
distancing, face coverings, fever scanning, and even tests for anosmia should
be continued alongside ADM.
Noise
Attention must be given to the problem of noise associated
with air management. Tubes will be of smooth
bore rather than corrugated. Valves will be made of soft material, and the points
of impact of valves will be designed to avoid noise. Air flow will be laminar,
and as slow as is possible compatible with amounts required for respiration.
Safety
There is a serious responsibility undertaken in supplying
air to hundreds of people. System integrity is vital since leaks in delivery
tubes could result in dust or poor-quality air being delivered. Highest quality
materials will be used, with levels of volatile organic compounds from the
constituent plastics being kept as low as practically achievable, so material
selection will be important. Potential breakdown in the system of delivery and
exhaust air management must be monitored with regular checks.
Indirect
positive effects of ADM
As knowledge of the testing aspect of ADM becomes general,
people who are suffering symptoms of Covid-19, or who know that they have been
in contact with the disease, will be inhibited from going out into crowded
places for fear of being identified in public.
Conclusion
There is a strong case, both from a public health and a
financial viewpoint, for venues management to consider which form of Air Dynamics
Management would be most appropriate for their venue, and to set about installing
it. Similarly, there is a strong case for manufacturers of air management
equipment to set about designing, producing and marketing such equipment.
ADM delivery system
Figure 1
The author
Dr Richard Lawson MB BS, MRCPsych
is a retired general practitioner of medicine, author of Bills of Health
(Radcliffe Medical Press 1996, ISBN 1-85775-101-9), poet (In the Key of Blue
(ISBN 978-1-78719-545-5), Green politician (Past national co-speaker, Green
Party of England and Wales), past elected Local Authority Councillor, and
inventor of physical technology (Aerosail, Phoenix bike stand, BrambleHook) and
social inventor (Green Wage Subsidy).
The author asserts, and has protected, the intellectual
property included in this paper.
rlawson@gn.apc.org
15/09/2020
