How it Works

WHAT WE DO 

The Short Story

Pure Skies system is a novel, effective technology that improves air quality over large areas. 

 

Particle pollutants - PM10 and PM2.5 - are the main target, and are typically reduced by 30-80% depending on their baseline levels. The higher the baseline values, the larger the degree of reduction. 


Certain gaseous pollutants - nitrogen oxides (NOx), sulfur dioxide (SO2), carbon monoxide (CO), are reduced by 20-40%, typically in the form of secondary PM2.5 or as aerosols. Atmospheric carbon dioxide (CO2) is reduced to a lesser degree - 10-40 ppm, again, depending on baseline values. 

Air quality index improves by a minimum 33%.

Unlike conventional air purifiers, Pure Skies does not use a fan or filters to clean small volumes of air. Instead, they use pulsed radio waves in the Wi-Fi spectrum (2.4-2.5 GHz) in specific pulsed sequences. This has the effect of accelerating the velocity of very small particle pollutants (< 20-30 microns) and aerosols, increasing their clearance through a natural process called dry deposition.

 

Imagine a billiard table (the atmosphere) filled with billiard balls (pollutants). When the cue ball (radio waves) hits the billiard balls, they move. In the hands of a skilled billiard player, the balls move quickly into the side or corner pockets and are cleared away (dry deposition). 

Pure Skies 9000 is designed for outdoor use in cities and heavy industries and is our flagship model.

 

Pure Skies 6000Pure Skies 5000, and Pure Skies 3000 are for indoor use. 

Each Pure Skies system consists of two components:

  1. The Air Pollution Control Equipment: One base station and one or more extender units, to create a point to point network. The base station consists of a circular polarized transmitter antenna, signal source, power source, internet of things (IoT) hardware for communication from our control room to the unit, an uninterrupted power supply (UPS), and miscellaneous hardware for electrical safety and security.  

  2. A 3rd party Air Quality Monitor (AQM) to measure local ambient air pollution levels, monitor system efficacy, and provide real-time feedback to optimize system function. 

HOW IT WORKS 

The details

Pure Skies pulsed radio waves in the Wi-Fi spectrum (2.4-2.45 GHz) using a custom made transmit-only polarizing omnidirectional antenna (EIRP 100-300 mW, gain 3-8 dBi).


Laboratory and field data suggests that Pure Skies accelerates the clearance of certain pollutants in the air, primarily through dry deposition. Dry deposition is the clearance or transport of particles from the air to the solid surfaces in the absence of precipitation. It occurs as a natural phenomenon by a combination of gravitational settling, electrostatic attraction, diffusiophoresis, impaction, interception, and thermophoresis.

What is dry deposition?

Dry deposition is the deposition of pollutants, including particulate pollutants and aerosols, as they settle out of the atmosphere or are absorbed by soil or vegetation. Gaseous pollutants can undergo dry deposition when they are absorbed by liquid surfaces or solid surfaces such as soil or vegetation.  

In nature, particles (or in some cases, aerosols) in the atmosphere are transported vertically by turbulent mixing and gravitational settling. As the particle is transported closer to the surface, the effects of Brownian diffusion and inertial impaction are comparable to the diminishing effect of turbulent mixing. Eventually, the particles are transported close enough to the surface to adhere. 

Dry deposition is distinguished from wet deposition, in which atmospheric chemicals and pollutants are deposited through the action of rain, fog, or snow. When sulfur dioxide (SO2) is removed by wet deposition, the result is acid range which causes widespread damage to ecosystems. 

How do pulsed radio waves affect dry deposition?

Based on laboratory data, we posit that pulsed radio wave technology takes advantage of the dielectric effect created under the influence of a spatially non-uniform electric field. The radio wave energy which is broadcasted in a pulsed manner generates a non-uniform electric field with the strength of the field varying inversely with distance from the antenna. The opposing ends of the dipole created within particle pollutants (under the influence of the dielectrophoretic force) experience slightly different forces. As a result, small particle pollutants undergo a net translational motion via the dielectrophoretic force. In other words, pulsed radio wave technology likely creates a weak electric field that affects particle pollutants of very small size (lab tested up to 20-30 microns in diameter), causing their motion to accelerate.

 

Unpublished data from our lab suggests that the reduction in ambient pollutants occurs through the agglomeration and settling of these particle pollutants, with a maximum size of 20-30 microns in diameter. This is supported by our observation using particle counters that particle pollutants of 100 microns in diameter are unaffected by pulsed radio wave technology, and that PM10 is reduced to a lesser magnitude compared with PM2.5. 

While our unpublished data is strong, we recognize that more work remains to be done in this area, and are actively pursuing this. 

 
What happens in the field (in real life situations)?

One of India’s leading NABL accredited and MoEF approved testing laboratory with 31-years of experience in Environment, Food, Pharma, and Construction Materials, evaluated the Pure Skies technology, independently of Devic Earth. 

What they did. A Pure Skies base system was installed on the rooftop of a 4 story building in the Mayapuri area of Delhi. Because this is an area with predominantly low rise buildings, the range of Pure Skies would be expected to be far. The test laboratory installed several reference grade air quality samplers placed 2-km away according to standard siting methods for air quality monitors. Air quality measurements took place continuously over 3 weeks – an initial 1-week baseline, a second week with Pure Skies on, and a final week with Pure Skies off. Throughout the duration of the test, weather data and traffic patterns were recorded to correlate with pollution levels. The test took place in June 2019. All data recording and analysis were performed by the test Laboratory.

The results. As expected for Delhi - even in June - baseline levels of PM2.5 and PM10 were high (see Figure below). After Pure Skies was turned on, PM2.5 and PM10 reduced by 65% and 28%, respectively, measured 2 km away. After Pure Skies was turned off, these values returned to their previous baseline values.

Meteorological parameters including wind speed, direction, precipitation, as well as traffic density, were stable during the testing period. 

3rd party test results of Pure Skies performed by a NABL accredited MoEF approved laboratory in Delhi. The two red shaded areas represent time periods when Pure Skies was off. The green shaded area represents the Pure Skies on period. Pure Skies reduced 24-hour levels of PM2.5 by 65%. After Pure Skies was turned off, there is a residual effect for 2-3 days, after which pollutant levels returned to their previous levels. PM10 levels reduced by 28% (data not shown). Note that there is a typical residual effect on pollutant levels for 1-3 days after Pure Skies is turned off, as seen during the first part of the period when Pure Skies is turned off. Data source: Reference grade ambient air quality monitors provided by test Laboratory.

Particle size matters

The magnitude of reduction is greater with PM2.5 than with PM10. This likely occurs because particle deposition velocities in dry deposition are size dependent. 

 

Based on scanning electron microscope data from our gas lab, pulsed radio waves have little effect on particles > 30 microns in diameter. These particles are simply too large for our technology.

Pulsed radio waves have no effect on larger particles such as PM100 and the larger components of coke dust, sand, and volcanic ash. 

 

The graph below demonstrates the types of pollutants based on size that are effectively handled with Pure Skies (shaded area to the left). We do not have adequate data on particles of 1 micron or smaller in diameter. 

Other pollutants

Ozone and certain pollutants (e.g. polyaromatic hydrocarbons) are not affected by pulsed radio waves. 

 
Air quality index improves with the Pure Skies system

Air quality index (AQI) is a measure of air quality used by governments and regulatory agencies to communicate to the public about how good (or bad) the pollutions levels are in a particular area. The higher the AQI, the worse the air quality and the increasing likelihood that public health will be affected. 

Different countries have their own air quality indices, corresponding to different national air quality standards. In general, the AQI is a composite of the 4-5 air pollutants that are of relevance to that particular country. Most commonly, these may include: ozone; carbon monoxide; nitrogen dioxide; sulphur dioxide; and particulate matter (including PM10 and PM2.5). 

A number of factors affected the AQI. For example, AQI will increase due to an increase of air emissions (e.g. rush hour traffic or when there is an upwind forest fire) or from a lack of dilution of air pollutants due to stagnant air (low wind speeds, temperature inversion, or anti-cyclone). Factors that improve AQI include increased wind speed, precipitation in the form of rain, snow, or storms, as well as pollution control measures such as improvements in vehicle efficiency, banning burning of garbage, etc.

The Devic Earth Pure Skies system reliably and safely improves the air quality index in the community in which it is placed, typically by 33%. Data from one of our installations inside an office space adjacent to a major arterial road in Bangalore in January-February 2019 is shown below. 

Improved air quality means better health 

A common question we get is, "Are there any adverse effects on human health from this technology?"

First, Pure Skies operates in the Wi-Fi spectrum (2.4-2.5 GHz) and follows all applicable laws and regulation for use of this spectrum. Extensive safety testing by independent laboratories has been done to ensure that we meet and exceed safety regulations with regards to radio frequency (RF) power, effective isotropoic radiated power (EIRP), and other common safety parameters used in telecommunications. 

To evaluate the effect of clean air with Pure Skies on public health, we evaluated the impact of our Pure Skies system on public health, by measuring the incidence of acute illnesses related to air pollution. We retrospectively evaluated 1,300 subjects presenting to a large tertiary care hospital in Bangalore where one Pure Skies system was installed. We found an overall 33% reduction in the incidence of acute illnesses amongst those people who lived in a 10 km radius from the system (see below).  

In the graph below, the blue and orange columns demonstrate levels of air pollutants or illnesses when the Pure Skies system is off and on, respectively. There is a corresponding decrease in incidence of acute illnesses related to air pollution (heart attack, respiratory illnesses, etc. when the Pure Skies system is on compared to when it is off. 

Limitations of the Pure Skies system

No technology can do all things. Important limitations of the Pure Skies technology, and some workarounds, are described below:

 

1. Pure Skies efficacy decreases with increased distance.

This is analogous to a cell phone tower. Generally, cell phone signal is good when you are close to a tower and decreases as you move farther away. Since Pure Skies works similar to a TV or radio tower, its efficacy decreases with increasing distance (generally 10 km for Pure Skies 9000, depending on local topography). This happens because the power of the radio-frequency waves from the antenna decreases with distance.

2. Pure Skies efficacy is blocked by tall buildings or hills.

This happens for the same reason as in Limitation 1. Both of these limitations can be addressed by installing several Pure Skies systems across a large geographic area, typically on building rooftops at 10 km distance from each other. Installing the systems at greater heights (e.g. on a cell phone tower) does not make a quantifiable difference in system efficacy. 

3. Pure Skies is designed for ambient air pollutants.

Pure Skies does not affect emissions inside a flue stack (or vehicle tailpipe), where particle velocity and temperature are typically much higher than that seen in ambient air. 

4. Pure Skies does not reduce smoke from fire or welding fumes. 

These fumes and/or soot are initially at high temperatures, and must cool from a gaseous phase to a (transient) liquid phase to a solid phase. Once these pollutants disperse in the air, then Pure Skies can begin to take effect. 

5. High humidity has a mild effect on efficacy (it's not the heat, it's the humidity...)

Pure Skies efficacy is reduced by 10% when humidity is high (> 70%). 

A DECADE OF R&D

Our Pure Skies technology has been under active R&D by Devic Earth’s co-founders since 2008, with collaboration from environmental chemists and physicists in the USA and India.

 

Funding for our research work has come from the Ministry of Environment, Forests, and Climate Change, as well as several industries and a number of private foundations.

 

We are actively engaged in basic and applied research, and have submitted our first round of manuscripts to peer reviewed journals for review. 

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