Getting Odd-Even Right - Lessons from Beijing, Paris, and London

We know by now that air pollution is not a standalone problem in a city but is essentially a symptom of inadequate planning. Policymakers can implement one-off solutions against air pollution but the best short-term results are possible only when they are fully implemented with no exemptions. One example is Beijing during the 2008 Olympics. Based on satellite observations, and during the two months when stringent restrictions were in place, the levels of nitrogen dioxide resulting from fossil fuel combustion plunged nearly 50% and the levels of carbon monoxide fell by almost 20%. The measures were good at quickly lowering the pollution but since they weren’t addressing the root problem, they could do nothing once the stay order was lifted. The battle against air pollution in Beijing recently led to an announcement of ‘anti-smog police force‘ and an expenditure of $2.6 billion to bring back clear sky days to the city.

The measures introduced in Beijing have become somewhat of landmark examples to achieve quick mitigations. These include a 50% cap on vehicles everyday based on the registrations, full support from the public transport sector, shutdown of industries and power plants within a radius of 100 km for at least a month before the games began and a strict enforcement of a ban on burning coal and biomass for cooking and heating. It was a matter of national pride; every citizen in the city chipped in to make sure the sky was blue and the air was clear.

The most talked about scenario is the 50% cap – a.k.a. the odd-even program. Key features that led to the program’s success were limiting the exemptions to emergency vehicles, thousands of number plate recognition cameras to aide traffic police and a wide network of railways and roads to take on the additional load. This was a proactive measure, knowing that air quality during the games would be bad but had to be better.

In 2016, the Delhi government played with the odd-even theme twice, for two weeks each in January and April, with a lot of exemptions and even a temporary increase in public transport capacity. Neither pilot pointed to a clear reduction in pollution. The reasons are plenty: the share of pollution from other sources is equally significant; the prevalent weather brought down pollution from the fires in Uttarakhand and there is limited information to statistically argue for success. General reports showed lesser congestion, faster speeds on the road and 13% more daily revenue for the Delhi Transport Corporation.

In December, 2016, Paris also implemented an odd-even program, in advance, due to an anticipated red alert for the city, and to make the program a success, made all public transport modes free. Their biggest advantage is that transport is their only big source of pollution in the city, followed by coal and wood burning for heating purposes, which means cutting down the traffic by 50% and a wide media campaign to alert people to not burn coal or wood, but use electricity for heating, gives them immediate benefits.

Read more on this @ the WIRE

Delhi's Graded Responsibility Action Plan (GRAP)

Delhi is in the middle of its worst air pollution episode in 20 years, which led for the first time in its history to close thousands of schools for more than three days. In December 2016, Delhi proposed the Graded Responsibility Action Plan (GRAP), a series of measures to call under poor, very poor, severe and emergency polluting conditions. This was approved by the Supreme Court, giving the Environment Pollution Control Authority (EPCA) the authority to oversee implementation for the National Capital Region (NCR). The highlights of GRAP are (download PDF):

• For moderate to poor conditions, with concentrations ranging between 61 and 120 μg/m3 for PM2.5 and 101 to 350 μg/m3 for PM10, actions include ensuring strict enforcement of controls on garbage burning, brick kilns, power plants, ash ponds, construction sites, fireworks and periodic wet sweeping of roads; vigilance on polluting vehicles, vehicles touting PUC norms and out of state trucks; deploying more traffic police; and posting information on social media
• For very poor conditions, with concentrations ranging between 121 and 250 μg/m3 for PM2.5 and 351 to 430 μg/m3 for PM10, actions include banning diesel generator sets, increasing parking fees, increasing bus services, stopping coal and wood burning at hotels, opening eateries and stationing guards at markets in residential areas; increasing public awareness
• For severe conditions, with concentrations above 250 μg/m3 for PM2.5 and 430 μg/m3 for PM10, actions include shutting down brick kilns, hot-mix plants, stone crushers, Badarpur power plant, intensifying public transport services and wet-sweeping roads more frequently
• For severe and emergency conditions, with concentrations above 300 μg/m3 for PM2.5 and 500 μg/m3 for PM10 for more than 48 hours, actions include closing entry of non-commodity trucks, closing all construction, introduction of odd-even and additional measures as the authority’s see fit.

Read more on how to improve GRAP @ the WIRE

Need Proactive Planning to Avoid Air Pollution Emergencies in Delhi

 

Read the full article @ Times of India

An excerpt from my commentary in the WIRE


All these examples (from Beijing, Paris, and London) and (various) pilots show only one thing: when pollution is bad, we have to be on a higher alert and have to do more than normal. We have to be more informed about the problem in advance and promote programs that avoid, improve, shift, just the way fuel is burnt in the city. For the GRAP program to succeed, two additional activities must be implemented on the ground:

• An immediate increase in the number of continuous air monitoring stations (CAMS) in NCR. The number of stations operational under CPCB, Delhi (13), Faridabad (1), Gurgaon (1), Rohtak (1) and Noida (1 – proposed), are not enough to support the GRAP program. Given the ranges of pollution we have observed in the last decade and the mix of pollution sources in the region, our best guess is that NCR requires as many as 100 CAMS, reporting data on all the criteria-pollutants in real time. If the expansion of CAMS on a short notice is an issue, then the emerging low- and medium-cost sensors for key pollutants like PM2.5 and NO2 must be considered in order to be better informed of ground realities
• A proactive pollution alert system must be in place that will allow EPCA to notify agencies responsible for implementing GRAP at least 48 hours in advance. This goes hand in glove with the previous point – more informed we are about the problem, the more able we will be in avoiding it.

Road Dust in Delhi

@ Hindustan Times -  “The major problem faced by Delhi is of particulate matter,” says Mukesh Sharma, a professor at IIT Kanpur and lead author of a study about the sources of air pollution. The study found that road dust makes up more than 50% of the total PM10 particles, that are 10 micrometres or less in diameter, and about 38% of PM 2.5 particles (that are 2.5 micrometres or less). PM10 and PM2.5 levels in Delhi regularly rise to five the times safety mark. According to the US Environmental Protection Agency road dust is “earthen material or dirt that becomes airborne, primarily by the friction of tires moving on unpaved dirt roads and dust-covered paved roads”. With about 33,198km roads and nearly 97,04,741 registered vehicles, the wheels on the city’s poorly maintained roads grinds up a dust storm.

Also see "what's polluting Delhi"

Infograph - Penetration of Particulate Matter in Our Body

 

@ Camfil_UK

Also see "what can you learn from the chemical composition of particulate matter?" 

More on "how to study particulate matter"

Air Quality in Delhi (daily updates)

This is modeled source contributions to the ambient particulate pollution (PM2.5) in South Delhi district (one of the 14 districts in the National Capital Region (NCR) of Delhi). The calculations are conducted in forecast mode. More NCR district reports @ Delhi Air Quality.Info

• DUST.ERO = wind blown dust from the dry and arid regions, dependent of hourly meteorological conditions
• OPEN.FIRES = open biomass burning (both agricultural lands and forest areas), a seasonal affair linked to dry conditions and agricultural clearing patterns
• TRANS.PASS = contribution of passenger vehicles (2Ws, 3Ws, 4Ws, Taxis, and Buses)
  
• TRANS.FRGT = contribution of freight vehicles (heavy and light trucks, and non-road vehicles)
• RD.DUST = contribution of re-suspended dust on the roads due to vehicle movement and construction activities
• PP.DGS = contribution of power plants and in-situ diesel generator sets
• INDUS = contribution of industrial activities
• HOUS.HLD = contribution of domestic cooking, space heating, water heating, and lighting
• WST.BURN = contribution of open waste burning

• OTHERS = contribution of aviation, shipping, biogenics, etc..

A number of source apportionment studies were conducted in Delhi (more in Delhi than in any of the other Indian cities). We summarized the known particulate pollution source apportionment studies, as an open article, "what's polluting Delhi's air". A snapshot of the shares from one of the studies is presented below.

The modeled particulate pollution in the forecast mode for the next three days is presented, as time series for SO2 and Ozone for the district and as an animation for all PM2.5 covering the modeling domain. Similar animations and daily average concentration maps for all the criteria pollutants are available @ Delhi Air Quality Info

See what is happening at the regional scale, which is conducted as part of the all India air pollution forecasting program, hosted @ https://www.indiaairquality.info. The animation below is from a WRF-CAMx simulation conducted @ 0.25x0.25 degree resolution (approximately, 25km x 25km).

The pollution patterns change every hour and every day, depending on the prevalent meteorological conditions - wind speed, wind direction, temperature, and precipitation. Under windy conditions, most of the emissions get dispersed to farther places; Under rainy conditions, most of the emissions get drained out. Want to see how the weather pattern is holding up for the next three days in Delhi. Check out @ https://www.delhiairquality.info. Below is an animation of the anticipated wind speeds and wind directions from the WRF meteorological model - also used by IMD for their forecasts.

The monitoring data from the DPCC stations reported as an air quality index by AQICN is as follows for one of the stations

Mapping Air Pollution Sources in Ulaanbaatar

Mongolia's capital city of Ulaanbaatar has its share of tourist attractions - Genghis Khan Square, the National Museum, the State Opera and Ballet Theatre. But Ger Community Mapping Center guide Tuguldur Chuluunbaatar wants to highlight a different part of the city; a part that's often ignored. "It's not like an entertainment or tourism tour," our guide Tuguldur Chuluunbaatar says. "It's more like giving people more realistic information about Ulaanbaatar, especially ger area."

Gers, or yurts, are the traditional circular tent homes used throughout Mongolia. In recent years, desertification and harsh winters called "dzuds" in Mongolian have forced thousands of rural Mongolians to pack up their gers and head to Ulaanbaatar in search of work. But the steady influx of people has caused serious environmental problems for the city. Since new urban residents burn coal to heat their yurts, the air quality in Ulaanbaatar has gotten worse than Beijing or Mumbai. In 2016, a nongovernmental organization called the Ger Community Mapping Center started working to get a handle on these problems - through mapping.

Read the full article @ DW

More news and articles on air pollution in Ulaanbaatar

The National Capital Region of Delhi Requires At Least 100 Air Monitors

When pollution is bad, we have to be on a higher alert and have to do more than normal. We have to be more informed about the problem in advance and promote programs that avoid, improve, shift, just the way fuel is burnt in the city. For the GRAP program to succeed, two additional activities must be implemented on the ground:

• An immediate increase in the number of continuous air monitoring stations (CAMS) in NCR. The number of stations operational under CPCB, Delhi (13), Faridabad (1), Gurgaon (1), Rohtak (1) and Noida (1 – proposed), are not enough to support the GRAP program. Given the ranges of pollution we have observed in the last decade and the mix of pollution sources in the region, our best guess is that NCR requires as many as 100 CAMS, reporting data on all the criteria-pollutants in real time. If the expansion of CAMS on a short notice is an issue, then the emerging low- and medium-cost sensors for key pollutants like PM2.5 and NO2 must be considered in order to be better informed of ground realities
• A proactive pollution alert system must be in place that will allow EPCA to notify agencies responsible for implementing GRAP at least 48 hours in advance. This goes hand in glove with the previous point – more informed we are about the problem, the more able we will be in avoiding it.

Read the full article @ the WIRE on how to improve the Graded Responsibility Action Plan (GRAP) for better air quality in Delhi.

Delhi to Get 10 New Monitors in Winter 2017-18

The top court in December last year had asked authorities to install real-time and manual pollution monitoring stations in Delhi, Haryana, Uttar Pradesh and Rajasthan to check air quality for the graded response. According to the SC-approved graded action plan, the entire national capital region (NCR) will be treated as one. Authorities and experts have warned that the landlocked city’s air quality cannot improve unless adequate measures are taken in the whole of NCR, which involves territories governed by neighbouring Uttar Pradesh, Haryana and Rajasthan. Read the full article @ Hindustan Times

Infograph - Comparing AQI Scales for PM2.5

More on the simple tools for air quality analysis @ http://www.urbanemissions.info

TED Talks - Cars Almost Killed Our Cities, But Here's How We Can Bring Them Back

Our cities are making us – and the planet – sick, and the problem lies in the automobile, which has taken over how we live and use space. Thankfully, new technology like autonomous vehicles and 3D printing has opened the door for us to bring our cities back from the brink, says transportation expert and city planner Gabe Klein. But we need to act quickly to ensure cities will be places we want to live.

TED Talks - How to Fight Road Congestion (Case Study of Stockholm)

TED Talks - It's an unfortunate reality in nearly every major city—road congestion, especially during rush hours. Jonas Eliasson reveals how subtly nudging just a small percentage of drivers to stay off major roads can make traffic jams a thing of the past.

Video - A clean 101 Lecture on Global Climate Change

More @ Bozeman Science

Infograph - Meteorology in Delhi

more on meteorological forecasts and archives, please visit http://www.delhiairquality.info

Infograph - Prevalent Wind Directions in 16 Indian Cities

This is based on the WRF-NCEP simulations for year 2015. More information on other key meteorological parameters affecting air pollution is at http://www.indiaairquality.info

Diesel to Electric Switch for Buses Dropped NOx Levels by a Third

The switch from diesel to electric buses and reducing deliveries to the street’s hundreds of shops is said to be behind the fall in nitrogen dioxide levels. The Mayor of London, Sadiq Khan, has welcomed the clean-up but said there is still a long way to go until the street meets legal air quality levels. He said: “The improvement in Oxford Street’s air quality is welcome news and testament to the changes that we have been making not only in this area, but to the entire bus and taxi fleet in London. “This is only the beginning and there’s still a lot more work to be done in the battle against London’s toxic air.”

Around 262 buses travel down the busy route every hour and Transport for London have ensured 70 per cent of vehicles either have electric or greener engines. Readings taken by King’s College London and London Air monitors show nitrogen dioxide released by vehicles was 135 micrograms per cubic metre of air in 2015, compared to 86 micrograms per cubic metre in 2016 - a drop of around 30 percent. The street is still in breach of EU regulations on the number of hours each year it can surpass pollution levels, but it is making significant progress. In 2015 safe pollution levels were breached for 1391 hours, and in 2016 this dropped to 163 hours - a decrease of 88 per cent. Tim Baker from the Environmental Research Group at King’s College London said: "The data for Oxford Street for 2016 is still provisional and needs to be analysed very carefully to determine exactly which changes had an impact and when.

Read more @ Evening Standard

Infograph - How to Apportion the Role of Emissions and Meteorology to the Growing Air Pollution Problem in Delhi?

72 hour forecast of the mixing heights over the Greater Delhi region

Hourly mixing layer height was simulated using the 3D-WRF meteorological model and the GFS meteorological fields for the next 72 hours. The modeling domain covering Delhi and its satellite cities, extends 80 km in North to South and 80 km West to East. The data fields are updated everyday at ~7:00 PM local time.

Ulaanbaatar's Pollution Through a Magnifying Glass

It’s 6:50 a.m. in the morning. I wake up next to my beeping alarm clock to see the usual blanket of smoke covering the city in my view through the window. With a cup of coffee in hand and its aroma enveloping the room, I look at the poetically beautiful but realistically lethal sight: smoky Ulaanbaatar. In the sky, a beautiful dark gray to blue gradient spans from the north to the south, and a navy blue streak is followed by a thick swatch of dark gray, and then by a softer gray from the sky to the ground.

The smell of smoke fills my nostrils and lungs as I take the first step out of what seems to be my safe haven, my home. It instantly triggers a minor headache. What we jokingly say often is that we Mongolians are a fast-adapting people, and that we’ve probably already adapted to the smoke. Some have uttered this phrase so much that they actually believe it themselves. According to E.Undarmaa, a teacher at the Mongolian National University of Medical Sciences, you don’t want your body to adapt to pollution. “It’s not even adapting, your cells are changing for the worse,” she says.

I instantly put on my air filtration mask, hoping to God it doesn’t ruin my makeup or that it doesn’t imprint itself on my face. The mask’s exterior seems to be resembling the gray shade I so often see every morning. I’ve only worn it for four days.

Read the full article @ UB Post

Video - How Cars Went from Boxy to Curvy and Why?

From TED-Ed

Inforgraph - How Carbon Capture Works?

@ Yale e360 - The first large-scale power plant in the U.S. that removes and stores carbon dioxide from coal combustion is now fully operating near Houston, Texas, capturing more than 1 million tons of CO2 annually. Operated by NRG Energy and JX Nippon Oil & Gas Exploration Corp., the Petra Nova plant — which cost more than $1 billion — extracts carbon dioxide from flue gases and then pipes them to the West Ranch oil field 80 miles away, where the CO2 helps extract additional oil from the ground.

The U.S. Department of Energy, which provided $190 million in grants to the plant, called the facility “the world’s largest post-combustion carbon-capture system.” A second large carbon-capture plant is set to become operational in Mississippi by the end of the month. The Kemper Power Plant is designed to turn lignite, a type of coal, into a gas called syngas, removing some of the CO2 before the syngas is burned to generate electricity.

Infograph - The Periodic Table of the Elements, in Pictures

 

@ elements.wlonk.com

Infograph - 1 Old Truck Pollutes as Much as 30 New Trucks

 

by MnPCA

Health Conscious residents Assemble in Shanghai to Share Ideas for Low-cost DIY Purifiers

Over the past several weeks, numerous cities across China have been blanketed with severe industrial smog. The year's very first Red Alert for heavy air pollution was issued in Beijing just three days into 2017, followed by a 212-hour Orange Alert. After making domestic and international headlines for its toxic smog, concerned Chinese citizens have been heatedly discussing and debating clean-air alternatives in lieu of any enforcement of government regulations.

For those who can afford costly air purifying machines, which can be as expensive as 10,000 yuan ($1,443), the solution is relatively simple. But is shelling out big bucks the only way to keep our air at home and the workplace fresh? Social enterprise Smart Air Filters recently held a workshop in Shanghai to inform residents with limited budgets about alternative DIY (do it yourself) options.

At the one-hour workshop, Noah Willingham, South China Head of Smart Air Filters, revealed that their company's founder, Thomas Talhelm, figured out that the primary components of a standard air purifier are nothing more than a fan and a High Efficiency Particulate Air (HEPA) filter.

Willingham explained that Talhelm purchased an average HEPA filter on Taobao, and then strapped the filter to a fan. The total cost was less than 300 yuan, and to his surprise this home-made purifier was just as effective in reducing PM (particulate matter) as the most costly machines.

At the workshop, Willingham brought the same HEPA filter along with a standard fan and installed the parts together in front of the audience to show how easy it is. He then used a PM counter to test the air quality around the filter, which was dramatically lower than elsewhere in the room.

Despite the low-price of a HEPA filter, some audience members pointed out that DIY air purifiers have minor disadvantages. For instance, 40-year-old Peng Peng said that the crude appearance of a DIY air filter doesn't suit her aesthetic tastes and is also quite noisy, which would affect her sleep.

Others pointed out that common houseplants such as the Snake Plant (Mother-in-Law's Tongue), palms, ferns and pothos (Devil's Ivy) are each very helpful in filtering out PM from household air. Indeed, many Shanghai-based consulates and corporations are now installing vertical "green walls" in their offices as natural alternatives to expensive, mechanized air filters.

Read the full article @ Global Times

Video - How to Measure real-driving Emissions Using Portable Emissions Measurement Systems (PEMS)

Vehicles are tested in controlled and relatively narrow laboratory conditions to determine their official emission values and reference fuel consumption. However, on the road, ambient and driving conditions can vary over a wide range, sometimes causing emissions to be higher than those measured in the laboratory. For this reason, the European Commission has developed a complementary Real-Driving Emissions (RDE) test procedure using the Portable Emissions Measurement Systems (PEMS) to verify gaseous pollutant and particle number emissions during a wide range of normal operating conditions on the road. This paper presents the newly-adopted RDE test procedure, differentiating six steps: 1) vehicle selection, 2) vehicle preparation, 3) trip design, 4) trip execution, 5) trip verification, and 6) calculation of emissions. Of these steps, vehicle preparation and trip execution are described in greater detail. Examples of trip verification and the calculations of emissions are given.

View the video and the full paper @ JOVE

Schematic Showing Haze and Smog Formation in Beijing

 

The research group led by WANG Yuesi from the Institute of Atmospheric Physics (IAP) has monitored the evolution of regional atmospheric mixing layer height (MLH) and attenuated backscattering coefficient in the Beijing-Tianjin-Hebei region for years. Combined with the particle's chemical component online analysis, some highlighted results about the regional heavy haze formation mechanism are obtained. "Beijing is located to the north of the North China Plain. More @ Eureka Alerts

Environmental Police Force in Beijing

One of the world's most polluted cities, Beijing will set up a green police force to contain pollution which has reached endemic proportions in the megapolis. Besides, the authorities will ban 300,000 high polluting vehicles and shut down the only coal-fired power plant and polluting factories in 2017.

Beijing will strengthen environmental protection in 2017 by organising an environmental police force to step up supervision and accountability in its 16 districts, the city's acting mayor Cai Qi was quoted as saying by Xinhua news agency on Saturday. "Open air barbecues, garbage incineration, biomass burning, dust from roads -- these acts of non-compliance with regulations are actually the result of lax supervision and weak law enforcement," said Cai at a meeting after a spell of smog lasting more than a week in the city.

Read the full article @ Business Standard

Smog in Chinese Cities

Why does smog keep blanketing Beijing? Smog in China has many causes, including pollution from industries and traffic, but it tends to happen more often in the winter, when plummeting temperatures cause electricity demand to soar. This pollution can come from many sources, but burning coal has been linked to the largest number of air pollution deaths in China, causing 366,000 premature deaths in 2013.

In the winter, more families are turning on their heaters—and most of the energy used to run them comes from coal-fired power plants that send tiny particles of charred dust into the air.

Those tiny particles, or particulate matter, are what turns clean air into smog. Particles in the air can reduce visibility and contribute to acid rain, which can damage vegetation. The particles can also discolor buildings, but the primary concern with particulate matter is what it can do to the human body. Particles smaller than 10 micrometers are of particular concern to health experts, as particles that small can damage the lungs, aggravate asthma, and even cause heart attacks. Inhaling particulate matter can even prove fatal for people who have existing heart or lung conditions.

Beijing's smog woes are compounded by an accident of geography, according to AccuWeather. Beijing is bordered by the Xishan and Yanshan mountains. When a high pressure weather system moves in, air near the city’s surface doesn't move up and over the nearby mountain ranges. It just sits there, getting more and more polluted, and residents keep breathing it in.

China is taking steps to address the issue. The government has restricted driving in an effort to staunch air pollution from cars. But that measure is temporary. Chinese officials announced this week that the country would spend $360 billion on renewable energy projects, amping up its reliance on solar and wind. But it has a long way to go. China is still the world’s largest consumer of coal by far, and plans to continue using the sooty source of power.

There is some cause for optimism. Like Beijing, Los Angeles also sits in a bowl-like depression, hemmed in by hills and sea—and like Beijing, it once had a serious smog problem. But strict regulations implemented over the past few decades have helped reduce the amount of smog in Los Angeles, bringing back blue skies. There’s hope that they could return to China too, though residents shouldn't expect to breathe easy any time soon.

Read the full article @ Popular Science

Infograph - Particulate Pollution (PM2.5) in India between 1998 and 2014

Data archive and maps are available @ http://www.urbanemissions.info

A Primer on Air Quality Management

A prerequisite to a air quality management plan is some idea of (a) how much is the pollution (monitoring trends) (b) where is the pollution coming (spatial trends) (c) who is contributing to the pollution (source trends) (d) when is the pollution (temporal trends) (e) what can be do about the pollution (control tends). This involves a long line of discussions, surveys, modeling, planning, and finally implementation of the decisions for better air quality. We put together an easy to read primer of these steps, an understanding of the players involved in the process, and how to start to think about managing the information for better air quality. You can download a pdf version of the primer here or browse the pages below

Stakeholders represented in the picture are from Aide Agency, Academics, Government, Industry, NGO, and a facilitator.

Pollution Creating Jobs in Delhi

The plastic curtains covering the “air pollution-free” bus stand at Delhi’s traffic artery on Vikas Marg, ITO flutter every time a vehicle passes by. For Bijoy Kumar Farida, 65, the curtains also keep the cold wind out through the night as he sits and “guards” three air purifier machines set up by a private firm as a CSR initiative to provide a “pollution-free” corner in the city. When commuters are long gone after 11 pm, he switches off the machines and huddles up under a blanket; a thick sheet on the metal bench his bed for the night.

“The machines give out very cold air. The temperature has dropped. It will get icy if they keep running,” Kumar says. He will switch the machines on if someone walks into the bus stand, but in the six days since he has been posted as a guard, he hasn’t seen anyone come between 11.30 pm to 5 am.

Also read - Delhi's plan for air filters is a red herring

The three air purifiers are attached to the metal bench using a chain and lock. Two men guard the machines in 12-hour shifts. “I sit right next to the machines. Even if I start to snooze, I wake up if someone comes close to the machines. They are expensive so I am always afraid of someone taking them away or damaging them,” says Kumar. The LED display on the stand shows the PM 2.5 levels inside and outside the bus stop. When they are off, the levels outside are as 345, and 132 behind the curtains. The figures change to 395 and 120, minutes after Kumar turns on the machine.

Read the full article @ Indian Express