What should schools do to prevent the spread of SARS-CoV-2 in classrooms – Part 2

In a previous post, I mentioned how important is to monitor the environmental conditions inside a classroom in order to minimize the spread of the virus. Temperature, relative humidity, particulate matter, and carbon dioxide values can serve as indicators, and thanks to them we can have an estimation of the possible propagation of the virus in a classroom.

It seems to me that most people and governments are convinced that the virus is in the air (finally), and although masks work (in most cases), we all know that it is difficult to demand from kids to wear them 8 hours a day without touching their face or each other. Definitely, the virus will affect the psychology of the kids in the classrooms, and most importantly their social skills.

In Madrid, Spain, the authorities have decided to install 6000 cameras in schools. I am totally against this decision. Are they going to fine a kid when he/she touches his/her face? Who is going to watch the footage from 6000 cameras in real-time to determine that a breach of the protocol has occurred? A complete waste of money as later they will have to remove them because of privacy concerns, mark my word on that.

We have to realize that is important to give “some freedom” to kids for their mental sake and for them to grow. Technologically, we can achieve that by offering them the best air possible. In my previous post, a colleague of mine told me that schools in Spain and schools in the UK are not the same because the weather conditions are not the same, and he is right. In south Spain, schools don’t invest in heating, and they could rely on window ventilation, but in the UK (and north Spain) because temperatures drop low earlier, schools need to invest in mechanical ventilation that will recover heat as well.

Either way and although I love an open window for fresh air, I recognize the need for mechanical ventilation systems that will introduce fresh and clean air to a classroom keeping particulate matter and CO2 low and at the same time temperature and relative humility at optimal levels for kids to study and teachers to work.

Hypothetical simulation: Fresh air comes from the back window and stale air exits from the front window, an asymptomatic student is sitting on the front row

The SARS-CoV-2 virus travels inside the tiny droplets we exhale while speaking, sneezing, or coughing. Those droplets aka aerosols have different sizes and can travel from a few centimeters to a few meters far. Most importantly, they can float and be suspended on the air for various minutes depending on their mass, increasing the chances of infection. The conditions inside a room play an important role.

Number and size distribution of the droplets exhaled by talking, sneezing, and coughing

Keep in mind, most of the time, we can’t see the exhaled aerosols below 50μm in diameter.

Currently, there is a lot of debate on which technology should be adopted by schools, medical centers, airports, etc in the area of the ventilation and air treatment as some of them offer some drawbacks.

You see, some of these technologies like pure UVC lamps, ion generators, or similar unregulated photocatalytic oxidation (PCO) technologies may produce a large concentration of unwanted gases like Ozone (O3), which is an irritant for the respiratory tract. CO2 is another by-product that may occur during the oxidation process. Many manufactures (but not all) regulate the concentrations of ozone their purifiers produce to safe levels.

Personally, I have a few important criteria to consider when it comes to which air purification/ventilation system a school should invest. First is the price, public schools can’t afford to install expensive HVAC systems. They need to reply on affordable solutions, and most likely systems that don’t require a lot of hassle to install and maintain (old building, poor infrastructure, no staff), the same applies to some private schools.

Secondly, the performance of the system (air volume m3/h) and the energy it uses (watts/h) must be optimal to keep the energy bill down and get the most out of it in each classroom.

Depending on how air ventilators/purifiers are designed and move the airflow in a room it may increase the chances of spreading the virus before removing it from the room. Simulations have demonstrated that downflow systems are more efficient than overhead systems. In simple words, we need to suck the air from the lower level in a room and introduce fresh and clean air from the top.

Hypothetical simulation: Fresh and clean air is introduced from the ceiling and the stale air is discarded from the vents below

There are so many options right now for someone to choose from. Standalone air purifiers, window ventilators with filtration systems, light fixtures that purify the air while they illuminate the space, central HVAC with quantum plasma that kills 99.9% of the viruses and up to 1000 m3 /hour C.A.D.R, or even special designed devices that can capture all type of particles in outdoor environments like a playground. I can’t tell you which one is the best because it depends on various parameters like the available budget, the infrastructure of the building, location, the size of the classrooms, and the number of students.

An expert is very important during the decision making to plan wisely and deliver the best air for kids. There are a lot of regulations regarding the air ventilation standards in buildings, and each country has its own. For example, in Spain, the UNE-EN 13779 states that a classroom of 45 m² with a height from floor to ceiling of 2.5 meters, occupied by 25 students and a teacher in primary school should renew the air 10.4 times in an hour.

  • 45 m³/h per person (IDA 2) x 26 people = 1,170 m³/h.
  • Classroom volume: 45 m² x 2.5 m = 112.5 m³.
  • Number of air changes in a classroom: (1,170 m³/h) / 112.5 m³ = 10.4 air changes in an hour

The same regulation states that the CO2 concentrations inside a classroom shouldn’t be above 500 ppm. Here come the real-time, low-cost indoor monitors that can measure constant fluctuations and warn teachers about the air quality in a room.


It will be very naive of us to think that only alcohol and masks (which not all of them are equally made) will protect our kids during the course of a day in a classroom. Most importantly, we have to think about their mental health too.

Below you will find a list of companies that have developed various systems for air ventilation and air treatment and each of them offer a different technology and experience.

Many thanks to all for the information you shared with me. Special kudos to caloryfrio.com

Risk of coronavirus transmission in different settings

Review: BRISE Multi-Shield Mask

Another great mask to wear against air pollution and the COVID-19 disease. BRISE the company behind the air purifiers just released the BRISE Multi-Shield Mask and they come in three different colours, Dark Black, Peach Red, and Sky Blue.

BRISE Multi-Shield Masks have some key characteristics that separate them from the competition. A certified filter against PM2.5 pollutants, which can block oily and non-oily pollutants, keep in mind that the most common N95 masks are not resistant to oil). Double water-resistant washable layer that can withstand up to 200 times of hand-washing by maintaining excellent filtration efficiency and long-term effectiveness. Finally, the organic cotton inner layer offers a gentle and comfortable touch to the skin.

The mask offers 3 layers of protection.Read More »

UV Filtration During COVID-19 with BRISE C200 Air Purifier (English/Español)

(Scroll down for the Spanish version/Desplácese hacia abajo para la versión en español)

Two years ago I reviewed the BRISE C200 and I have been using it everyday but I had never thought before that the UV sterilization process will come so handy. It provides an extra layer of protection in a house or in small office especially during this covid-19 pandemic.

I don’t know about your experience during the lockdown, but mine was quite frustrating when I had to go out for grocery shopping and return home or even when I ventilate my house. A lot of things had been written about the SARSCoV2 virus, like that it could survive on clothes, on surfaces (keys, phones, money, etc) and that it can be an airborne pathogen.

Airborne means that a virus is transmitted between people through respiratory droplets and contact routes.Read More »

Dear city of Almeria (Spain) or any other city in the world (English/Español)

(Scroll down for the Spanish version/Desplácese hacia abajo para la versión en español)

I am writing this article because I would like to help you understand the importance of the issue as the whole province and consequently my city Almeria doesn’t have an official air quality station with a sensor capable of measuring particulate matter with an aerodynamic diameter of 2.5 μm or less (PM2.5) in real-time.

What is Particulate Matter (PM)?

Particulate Matter (PM) are solids material (sometimes liquid too) that float in the air. Some PM is released directly from a specific source − combustion in Diesel engines − while others form in complicated chemical reactions in the atmosphere.

Particles in the PM2.5 size range can travel deeply into the respiratory tract, reaching the lungs. Studies also suggest that long term exposure to fine particulate matter may be associated with increased rates of chronic bronchitis, reduced lung function and increased mortality from lung cancer, and heart disease. People with breathing and heart problems, children and the elderly may be particularly sensitive to PM2.5.

The Problem

In the province and city of Almeria, there are three Air Quality Stations that measure many pollutants one of which is PM2.5. Unfortunately, these sensors are outdated and the results we get are ONE daily average value which is basically useless in my opinion. Apart from that, we need to wait for a month to get the results back after filing a form. I guess the same thing applies to the 68 stations all around Andalucia in total.

Citizens need real-time data in order to take action and reduce their exposure to air pollution. They also need better tools and maps where they can visualise where pollution is in order to avoid harmful exposure. There are already many studies supporting the correlation between air pollution and COVID-19 cases.Read More »

Air Quality data that make sense for the average users

Have you ever used an app that will help you relax? Well I have, one of them is Apple’s Breathe app that can be found in the Apple Watch since WatchOS 3. The idea behind the app is that a steady breathing technique will help you relax and hopefully reduce heart rate pulses. Great app but I think Apple or any other developer should combine Air Quality (AQ) data with their breathing/meditation app.

In a mockup that I designed based on Apple’s Breathe app (I chose Apple’s Breathe app for its simplicity and effectiveness), I placed the Air Quality Index (AQI) information inside the app and depending on the AQ at that period the user will be prompted to avoid breathing deeply when the AQ is unhealthy or to adjust the duration when the AQ is good and start. In case the AQ is unhealthy a reminder will notify the user to come back for a breathing session later when the air is healthy enough for deep breaths.Read More »

COVID-19, Air Pollution and Global Disruption

I wasn’t planning to write an article about the Coronavirus but after WHO declaring it a pandemic and as I receive a lot of traffic from people who try to find a good mask to protect themselves from the disease I changed my mind and I wrote a few lines on how I see the whole situation.

Better Air Quality

As you may have already read a NASA satellite took some pictures in Mainland China before and after the outbreak of the Covid-19. The imagery illustrates air pollution and how the concentrations of air pollutants have decreased dramatically after people were ordered to stay in quarantine. The same thing happened in Italy as the government restricted the movement and most Italians stayed at home.

Italy air pollution before after covid19

The virus was able to achieve something that I and many fellow clean air advocates try to accomplish for quite some time now, to decrease air pollution in the urban environment.

The restriction of movement proves the fact that the majority of urban air pollution is anthropogenic and mostly due to inefficient transports. Diesel and petrol cars, old buses, vans, vehicle tires and many more. Vehicles don’t move around alone though, we are the drivers, as a result, we can do better.

Madness and misinformation

The madness of buying tones of toilet paper proves how humans are panicking and they are in a survival mode. They copy unconsciously others’ behavior, which is a primitive instinct, in order to make sure they are safe. Covid-19 is a respiratory infection which means it doesn’t mess with your digestive system.

Misinformation is a powerful tool for the exploiters who will say anything to you in order to scare you and of course to take your money. Read and listen to news from trusted sources and make sure you double-check them.

Don’t panic!

Wash your hands well, avoid touching your face and keep your personal belongings clean, like smartphones, computers, glasses, etc.


Face masks can offer a level of protection if they are well designed and of course, if you maintain them and keep them clean too. If a mask catches a virus, the virus can stay alive for hours and up to a few days.


Some believe that we have to isolate ourselves in a global scale in order to eradicate the disease, however, economically, I am not sure if we can afford it. In addition, spring is almost here (in my city temperatures are reaching 23°C) which makes it much more difficult for people to stay indoors.

I am not an expert in that area but what do you believe? Should we close all businesses and institutes for 2-3 weeks and stay indoors?

Comparison  Particulate matter vs virusDroplets SARS-COV-2

Review: IQAir Mask

If you read my blog frequently you will know by now that I am constantly trying to find a face mask that fits perfectly around my face and keeps my internal organs (lungs, heart, brain, etc) away from PM2.5+ pollution. I have already found a mask that does that in previous review but I wanted to try IQAir Mask because it looks even more comfortable and lightweight. Let’s find out!

Read More »

EGYPT – Air Pollution

Recently, I travelled to Egypt and I had the pleasure to visit and see many fantastic and immense monuments like the Great Pyramid of Giza, the Abu Simbel temples and many others. A fantastic journey through ancient Egypt which literally transfers you to this great ancient civilization.

It rarely rains in Egypt and the temperature in summer can easily reach 48ºC/118ºF. That said, the Sahara desert plays an important role in the climate and air quality of the country. Particulate Matter is the main natural air pollutant and impossible to combat.

Read More »

Cheap Face Mask, Worth it?

Over the years, I have reviewed some very good face masks on See The Air like the Cambridge Mask and Vogmask. The only backward is the price especially when you have to buy them frequently because you wash them often and you wear them a lot. There is a solution by using masks such as the AirGo which allows you to chance the filters and the neck warmer is durable and washable and the O2 Canada Respirator which allows you to change filter easily. However, I wanted to try a cheap and lightweight face mask for the summer which will cost around $3 and it will have the ability to use exchangeable filters because I want to be able to wash it once a week.

Read More »