Report on air conditioning in dental clinics
The safety measures recommended for the return to activity in dental clinics to prevent the spread of COVID-19
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Dental-Office.org has produced a report with recommendations on air conditioning, air purification, and aeration in the dental clinic area although the current evidence is extremely scarce and is under continuous review. Therefore, most international protocols recommend that each dentist consults his or her air conditioning provider to find out about the type of ventilation installed and possible filters.
In addition, all protocols, without exception, recommend minimizing the aeration of the clinical area by keeping the door closed and ventilating after each patient. These recommendations are accompanied by the use of high-flow suction, as well as absolute isolation. Likewise, many recommend the installation of some kind of ventilation and/or air purification system for cabinets without the possibility of natural ventilation or where it is necessary for climatic reasons.
In this report, the technical details according to the air conditioning, purification and aeration system, and all the existing literature on this subject are presented.
Introduction:
In this connection, and in view of the many questions raised by the
recommendation to "not use the central air conditioning (if it connects common areas with
clinical area)", the following technical details are necessary, assuming by
The Committee notes that these are only non-binding Recommendations as the current evidence is extremely scarce and under continuous review.
Based on the scarce scientific evidence available on the subject:
1) It is known that activities that generate aerosols could theoretically disperse the load
viral in the environment in which they are generated.
2) While aerosol transmission does not appear to be the primary route, however, it should not
be excluded.
3) Most international protocols recommend that every dentist consults
with your air conditioning supplier to find out about the type of
installed ventilation and possible filters.
4) Many protocols recommend using the air conditioner only in
ventilation/extraction and do not use in recirculation mode.
.
5) All the protocols without exception recommend minimizing the change of air of the area
clinic, keeping the door closed and ventilating after each patient. You are
recommendations are accompanied by the use of high-flow suction, as well as
absolute isolation.
6) Many protocols recommend the installation of some kind of ventilation system and/or
air purification for cabinets without the possibility of natural ventilation or in
that is necessary for climatic reasons. In these cases, the air renewal rate
recommended should be at least 6 volumes/hour (no recycling)
In relation to air conditioning:
1) In general terms, individual air conditioners do not ventilate the room: they take in the air
of the room and return it to the desired temperature.
2) At present, the use or not of air conditioning in a clinical area generating
aerosols, in the period of COVID-19, is not consensual:
- For some authors, air recirculation systems such as air conditioners
whether or not they are equipped with filters, should not be used to the extent
possible, in order to avoid the dispersion of the generated aerosol to the whole clinical area.
- For others, on the other hand, the filtration provided by
(equipped with appropriate HEPA filters, however) could reduce the
airborne concentration of SARS-CoV-2.
3) For the use of HEPA filters, some protocols recommend that these be
category H13 or higher
4) If the air conditioning system is used, it is recommended to change the filters periodically
(ideally every week)
.
5) If air conditioning is used, it is recommended that it be used outside of the periods in which
that aerosols are being generated or when hygiene is being carried out,
disinfection and subsequent aeration.
6) In the case of using air conditioning, the instructions on temperature and humidity must
to watch and respect each other.
7) It is important to know that at room temperature of 21ºC, the degree of humidity is very
important in the survival of the coronavirus. If we increase the relative humidity
by going from 30% to 50%, we're doubling the survival time of the virus.
8) An internal environment between 21-23ºC in winter and between 23-25ºC in
summer. The relative humidity should try to stay between 30-50%. The lower the relative humidity the lower the survival of the virus, but also
The greater the dryness of the mucous membrane, the greater the risk of respiratory problems.
With regard to the so-called air purification:
Despite the diversity of offers in this field, there are no studies that compare the
efficiency and the benefits of systems to each other, nor a study of the variables (conditions) in
the field of the dental office as well as the side effects and risks inherent in
their use (Level IV, Class IIb).
Due to this lack of comparative studies properly applied to the dental and
to the dynamics of market supply at this time, many of the protocols
International experts recommend caution in the selection and adoption of a system of
Purification of the ambient air.
These air purification systems work, either through some
"trapping" (e.g. HEPA filters), either through oxidation techniques or
viral destruction (e.g., ultraviolet rays) Sometimes they have both techniques
combined.
There are many questions, some unresolved, regarding the possible use of
these devices :
- Is the safety of the device guaranteed? Some devices may degrade
the quality of the air and to originate pollutants and nanoparticles.
- Depending on the volume of the clinical area, the time needed to obtain the
Is the alleged efficacy compatible with clinical practice? Let's not forget that these
devices are generally less effective the larger the volume.
- Is the promised efficacy supported by studies with viruses
encapsulated?
- Some devices require that no one be present in the area being subjected to
process for a certain time.
- What has the initial investment and maintenance cost?
- At present, there are no clear and precise recommendations regarding these
devices against COVID-191
Based on expert opinion (the only source of the level of evidence available, Level
IV):
- This type of device is only complementary to the correct ventilation of the
clinical area and the adequate adoption of protection with PPE.
- The use of natural ventilation is considered a priority, although if it is essential
to use ambient cooling machines, slow flows and
These devices must be included in the cleaning and disinfection protocols of the
establishments, as they can collect particles just like any other surface.
- One piece of advice from health authorities is that
The air conditioning should not be used for recirculation of air if possible.
- It is advisable to reinforce the cleaning of the air conditioning filters before use,
in order to prevent the spread of viruses.
- In the case of centralized computers that cannot be shut down, the
recirculations, working exclusively with outside air.
- In order to facilitate the ventilation process, the operation should be programmed to be
hours before opening and also keep it for a while after closing.
- It should be remembered that, in the specific case of dental clinics, due to change of air
the recommended air renewal rate should be at least 6
volumes/hour.
- The filters must be cleaned and/or renewed, exclusively by technical personnel
authorized due to the high risk of contamination involved in handling
the same ones.
