Graph: Map of the epidemiological situation
Live. News about the coronavirus
It has been shown that the risk of airborne transmission by the SARS-CoV-2 virus inside buildings is higher when there is poor ventilation.
In this context, and since it begins to "scratch" to have the windows open all day, HEPA filters are trending topic.
They have been fulfilling their function in operating rooms or on airplanes for years but in recent weeks they have been proposed as a solution "for all audiences" in schools, in offices or in our own home.
Are HEPA filters the solution against coronavirus?
Before launching into the giant Amazon (for less than 100 we will find devices that promise to clean your house from coronavirus and fill it with unicorns) it is convenient to know how a HEPA filter works so that the investment we make is really useful against the coronavirus.
Ventilate: the mother of the lamb
The Government has published recommendations on the use of air conditioning and ventilation systems to prevent the spread of COVID-19.
According to the guide, the most important parameter in ventilation is air renewal per occupant.
As a recommended value, even in commercial establishments, a minimum of 12.5 l / second and occupant is established.
The point is that to guarantee this degree of air renewal at all times we should have specific outdoor air treatment units, something that ordinary mortals do not have at home or at our children's school.
Our options are mainly to take two measures: increase ventilation or reduce occupancy.
This is where our problems begin and we look for solutions.
Opening windows: an effective resource
When the building does not have mechanical ventilation systems, the guide of the Ministry for the Ecological Transition and the Demographic Challenge recommends the opening of accessible windows, favoring cross ventilation so that the contribution of outside air is the maximum possible.
Although it may generate some discomfort due to air currents, or the thermal sensation is not appealing, it has been shown that the renewal of air by cross ventilation lowers the rates of pollutants in rooms.
In fact, regular window ventilation is advisable even in buildings with mechanical ventilation.
eye!
These measures are as necessary for the prevention of the coronavirus as they are not very efficient from the point of view of energy efficiency.
Working on the environmental impact that these measures may have is something that we cannot ignore either.
What if there are no or insufficient windows?
In the case of places where it is difficult to ventilate, the Ministry recommends the use of portable units equipped with high-efficiency HEPA filters and place them in the spaces to be treated.
HEPA filters have the ability to retain aerosols in percentages greater than 99.95%.
Now, it is not enough to buy a device that lists "HEPA filters" on its box and happily install it in a corner of the classroom.
First of all, we must know that in Spain there is a regulation regarding HEPA filters, the UNE1822 standard.
It is important that the device
Meet the standard to ensure highly efficient air filtration.
According to the Federation of Indoor Environmental Quality Companies (FEDECAI), unfortunately, most air filters that are sold in a portable way for rooms (and that are attractive because they are really cheap) are not effective enough.
HEPA filters: more than a "little gadget"
In addition to complying with the standard, the effectiveness of this equipment depends on its correct selection and dimensioning for the place where it will be installed.
In an operating room or in an airplane equipped with HEPA filters, the ventilation system is designed so that all the air from the outlet passes through the duct where these filters are located.
In the case that currently worries citizens the most, that is, that of classrooms or offices where this prior design does not exist, it is essential that before buying and installing the device certain parameters such as the size of the room or the number of occupants of the same.
These estimates must be made by a competent technician, since, if the filter is not able to renew the air in the room at a sufficient speed, our investment will be ineffective and we will have made a bread like cakes.
In this regard, the location of the device is also important, as the air flow through the filters is limited.
Only the air in the area closest to the appliance may be "cleaned".
The area of the room where these devices can be effective is usually quite small, typically less than 10 m2.
Experts insist that increasing regular ventilation is often much more efficient as it also renews the air that comes from outside.
A separate chapter, but no less important, is to guarantee a good maintenance of the device, if the filters are not replaced properly and become saturated, they cease to be effective.
Purifiers?
HEPA filters with UVC lamps?
With regard to possible damage, although devices with mechanical HEPA filters are "harmless", there are air purifiers with different filter technology that can produce ozone in a secondary way.
There are also other devices combined with UVC radiation.
In particular, the Ministry's guide recalls that equipment based on ozone generation cannot be used in places with the presence of people.
On the other hand, both the health authorities in Spain and the World Health Organization have warned against the use of UVC lamps to disinfect hands or any other surface of the skin.
Therefore, although these combined devices can be useful in the professional field, they are not recommended for use in domestic environments where people are present.
HEPA filters, yes or no?
It is important to assess portable devices with HEPA filters for what they are: not a panacea, but a complementary measure that, well used and under the advice of a specialist, is useful, but does not exempt from continuing to respect other measures already
known as wearing a mask, keeping your distance, or mechanically ventilating.
These devices alone cannot guarantee adequate air quality, particularly when ventilation is insufficient and when there are significant sources of pollutants (in this case it can be a large number of people).
And of course, these devices also do not prevent the person-to-person transmission path, just as much more sophisticated ventilation systems do not.
If people who buy these devices are not clear about these issues, in some cases they could create a false sense of security and limit the use of other, more effective measures.
HEPA filters yes, but with professional advice, combining it with manual ventilation whenever possible and without neglecting the rest of the measures.
According to the criteria of The Trust Project
Know more
Science and Health
Covid 19
Coronavirus
China
Office How many people will have to be vaccinated to control the Covid?
This is how the vaccine race goes: safety, before speed
Interview "This is a warning. We are lucky, this virus is only 1% deadly"
See links of interest
News
Translator
Programming
Films
Topics
Holidays Madrid 2021
Confinement Madrid
The opening time trial of the Giro d'Italia, live: Monreale - Palermo
Real Valladolid - Eibar
Chelsea - Crystal Palace
CRI: Monreale - Palermo, live
Atlético de Madrid - Villarreal