Air Quality in the Rainy Season under WELL V2​

By RISC | 1 month ago

During the rainy season, one of the challenges we face is the increased humidity, which can lead to health issues if not properly managed.​​WELL Building Standard Version 2 (WELL V2) is a global standard for the health and well-being of building occupants. The standard has comprehensive guidelines for effectively managing humidity.​​High humidity in buildings can affect their users in several ways:​o Mold Growth: Excessive humidity is a key factor that promotes mold growth, which can lead to respiratory problems and allergies.​o Deterioration of Indoor Air Quality: The accumulation of dust and allergens worsens indoor air quality.​o Discomfort: High humidity levels can make people feel uncomfortable, sticky, and uneasy.​o Material Degradation: Excessive humidity can accumulate in building materials, damaging furniture, construction materials, and electronic equipment.​​To ensure that everyone using the building breathes clean and safe air, the WELL V2 provides specific guidelines for humidity management, focusing on:​ Thermal Comfort Concept - T07 Humidity Control: WELL V2 recommends that mechanical ventilation systems should maintain the relative humidity (RH) in buildings between 30% and 60%. The systems used may vary based on the size of the building:​o Residential Homes: Air conditioners with a humidity control mode (Dry) or an Energy Recovery Ventilator (ERV) system should be installed. ERV systems help exchange heat and moisture between indoor and outdoor air, conserving energy while maintaining humidity balance. Additionally, dehumidifiers can be used in combination with ventilation systems.​o Large or Public Buildings: A Dedicated Outdoor Air System (DOAS) can be employed to adjust outdoor air quality before bringing it into the building, including humidity control.​Moreover, WELL V2 recommends regular air quality monitoring, especially during the rainy season when humidity levels rise. Air quality data should be displayed on tablets or applications, with readings updated at least every 15 minutes.​ Moisture Management - W07 Water Concept focuses on reducing leaks and moisture accumulation:​o Building Envelope: To prevent moisture accumulation on the building’s exterior, areas should be designed with good drainage systems, regular inspections of rainwater drainage, and materials such as waterproof sheets, metals, or closed-cell foam that do not absorb water should be used.​o Interior Spaces: For areas with high moisture exposure, such as kitchens and bathrooms, moisture-resistant materials should be selected. It is also important to check plumbing systems to ensure there are no leaks, which could lead to moisture buildup. This includes inspecting toilets, washing machines, and dishwashers. Wastewater treatment systems and pipes should also have backflow prevention systems installed.​o For large and public buildings, a moisture control plan should be in place. This includes scheduling regular inspections for leaks, water damage, mold growth on walls, floors, and HVAC equipment. There should also be regular assessments of pipe leakage, and building users should be able to report leaks or mold directly. Additionally, WELL requires that leak inspection and mold reports be submitted to the WELL digital platform.​If we can effectively control and manage humidity during the rainy season, it will bring numerous benefits, such as:​o Improved Health for Building Occupants: Reduces the risk of allergies and respiratory issues.​o Enhanced Productivity: A comfortable environment promotes well-being and increases the productivity of building users.​o Cost Savings: Decreases repair costs from moisture-related damage and reduces energy consumption for air conditioning systems.​o Extended Building Lifespan: Prevents deterioration of the building structure and materials.​o Positive Image: Demonstrates a commitment to the health and well-being of building occupants.​​Implementing WELL V2 for humidity management during the rainy season not only addresses immediate concerns but also serves as a long-term investment in the health and sustainability of both the building and its users.​As consultants specializing in the WELL Building Standard, RISC have expertise in analyzing humidity issues and designing appropriate management systems in line with WELL V2 standards. We are ready to provide guidance and support your organization in enhancing humidity management to create a healthier and more efficient environment.​Let’s work together to create buildings free from moisture issues, ensuring a high quality of life for everyone in the organization, no matter the season.​​Story by Phetcharin Phongphetkul, Sustainable Designer/ LEED®AP BD+C, WELLTM AP, Fitwel Ambassador, ActiveScore AP, TREES-A NC, RISC​​References: ​Thermal Comfort Concept - T07 Humidity Control https://v2.wellcertified.com/en/wellv2/thermal%20comfort/feature/7 ​Moisture Management - W07 Water Concept​ https://v2.wellcertified.com/en/wellv2/water/feature/7 ​T07 Humidity Control Option 2: Humidity modeling https://v2.wellcertified.com/en/wellv2/thermal%20comfort/feature/7 ​A03 Ventilation Design https://v2.wellcertified.com/en/wellv2/air/feature/3A04 Enhanced Ventilation Design https://v2.wellcertified.com/en/wellv2/air/feature/6 ​A12 Air Filtration https://v2.wellcertified.com/en/wellv2/air/feature/12 ​01 Air Quality https://v2.wellcertified.com/en/wellv2/air/feature/1 Air Quality Monitoring and Awareness https://v2.wellcertified.com/en/wellv2/air/feature/8

Should We Enjoy the Weather in the Rainy Season?

By RISC | 2 months ago

We often hear people ask how nice the weather is. But how can we assess meteorological conditions for human comfort?​Thermal comfort is a good place to start.​Thermal comfort is being happy with our surroundings in terms of the body's heat. It depends on 2 key aspects: 1) physical factors in the surroundings and 2) individual factors. Environmental design should provide a comfort zone, not just mentally but also physically, neither too hot nor too cold.​So what physical factors in the environment affect comfort?​4 factors must be considered:1. Air temperature2. Relative humidity​3. Air velocity​4. Mean radiant temperature (MRT).During the rainy season, the air temperature drops. It mightn’t be comfortable, though, because the air is quite humid. (Read more here: https://bit.ly/3VjQysW) Our surroundings could be more comfortable if a wind is blowing. In a garden or on a lawn surrounded by trees and bushes, for example, there’s a low MRT value. We may feel cooler than when surrounded by concrete with a higher MRT, even if the temperature is the same.​In addition to comfort conditions, individual factors affect comfort. Everyone feels cold and heat differently, even in the same location. There are 2 human variables to consider:​1. Our outfit ​2. Our metabolic rate​In a hot and humid country like Thailand, a T-shirt and shorts seem cooler than a long-sleeved shirt and long pants. Clothing acts as an insulator, preventing the body's heat from transferring to the surrounding environment. To assess comfort, the thermal resistance coefficient of clothing, or Clo Value, is used. The body's metabolic rate is determined by the human activities that occur in that area. The body produces heat in diverse ways, which affects a person's feeling of happiness and comfort.​The Universal Thermal Climate Index (UTCI) is used in landscape design and building exteriors to quantify human comfort and thermal stress in a variety of situations. The calculation involves 4 physical parameters of the environment: air temperature, relative humidity, wind speed, and mean residual temperature. Temperature stress has 10 levels, with the median level or no thermal stress at 9-26 °C.​There’s lots more to learn about Thailand's environmental comfort characteristics. (Read more here: https://bit.ly/3VjQysW) There’s also been a lot of research into Thai people's comfort zones. Thais are accustomed to their hot and humid climate so could find different situations pleasant from other nationalities with different climates.​Story by Panpisu Julpanwattana, Senior Sustainable Designer and TREES-A Specialist, RISC​Reference ​Stein, B., & Reynolds, J. S. (1992). Mechanical and electrical equipment for buildings. New York: John Wiley & Sons.​

Putting up Mold- and Allergy-Free Wallpaper

By RISC | 4 months ago

Have you ever put up wallpaper in your home!​There may be risks hidden under the pretty colors. Thailand's hot and humid environment means that moisture accumulates on walls. Rainwater can leak in from the walls or roof. Broken water pipes can make the situation worse.​What’s more, using AC to keep your home at 25-27°C when outdoors is 36°C creates a relative humidity of over 60%RH, particularly in April. Condensation forms inside the wall depending on where the dew point temperature occurs when heat meets cold, just like fog on a window or water droplets on a cold glass. ​Chart 1: Psychrometric Chart displays a dew point temperature of 28°C when the outside air temperature is 36 °C and the relative humidity is 60%RH.​These issues result in moisture accumulating on house walls. We should avoid using additional materials to prevent it and instead go for a material that allows moisture to escape from the wall as fast as possible.​If the wall surface is decorated or other materials limit ventilation, such as wallpaper, issues with brick or concrete walls may be concealed. Particles and dirt behind the wallpaper will create fungus, resulting in air pollution, triggering allergic reactions. ​Figure 1: Condensation on building walls.​Figure 2: Mold on building walls is caused by coating the surface with substance that holds moisture. Figure 3 illustrates how to install wallpaper to reduce mold on building walls.​If you must use wallpaper to decorate your home, RISC has tips on material selection and installation techniques.​• To avoid dampness, examine and seal any leaks or cracks in the wall surface before allowing it to dry completely.​• Use a moisture-resistant foundation with antifungal ingredients.​• Select a non-toxic glue with low volatile organic compounds (low-VOCs) and no food-for-fungi additives. ​• Select breathable wallpaper and non-toxic ink to protect your health.​Wallpaper is not to blame if we can regulate our home's surroundings. To reduce the risk of fungus, avoid putting wallpaper in residential areas, particularly bedrooms, where environmental management is difficult.​Ultimately, think about when you last observed a difference in the walls of your home.​Story by Saritorn Amornjaruchit, Assistant Vice President of RISC

What can we learn from the chemical fire in Rayong?

By RISC | 4 months ago

The fire that broke out in a chemical tank in Rayong this month will likely have far-reaching impacts for property, safety, and the environment. Let’s look at what we learnt from the incident about dealing with dangerous substances.​Pyrolysis gasoline was stored within the tank. High-temperature decomposition of naphtha (naphtha cracking) produces olefins such as ethylene and propylene, which are precursors for making polymers and other plastics. But the process generates a byproduct known as pyrolysis gasoline, or pygas.​So how does Pygas affect our health?​Pygas is a hydrocarbon formed of many different components. Most of them are fragrant and have a high-octane value. As a result, it is frequently used to boost the octane amount of gasoline and serves as a precursor in the petrochemical industry. The gas is a volatile liquid classed as flammable. Its gas vapor is denser than air so accumulates at low levels rather than floating into the atmosphere. If the gas vapor travels into the air, it will harm everyone who comes into contact, causing eye and skin irritation, respiratory system problems, headaches, and nausea. Higher doses may result in unconsciousness.​When the gas ignites, it emits soot containing carbon monoxide. If inhaled, it will affect the respiratory system. Furthermore, excessive exposure produces a lack of oxygen, resulting in dizziness, nausea, vomiting, abdominal pain, chest discomfort, and shortness of breath. Higher doses will cause unconsciousness and may result in death.​What should we do if a fire breaks out?​​To extinguish pygas fires, use dry chemicals, sand, or foam rather than water, as the gas vapor might ignite and rise over the water's surface, causing the fire to spread further. Avoid regions where gas is distributed, including soot and smoke from combustion. Stay in a well-ventilated place and wear a mask to avoid breathing smoke and PM2.5.​Story by: Supunnapang Raksawong, Materials Researcher in Sustainable Building Material, RISC ​Reference:​Safety Data Sheet: Pyrolysis Gasoline, https://www.vitol.com/wp-content/uploads/2023/01/25.-Pygas_SDS_US_V3.0.pdf​

How Do Height and Temperature Affect PM2.5?

By RISC | 7 months ago

Many people believe that the higher you go, the cooler you get. But this isn't always the case. RISC is here to help explain.​We experience cooler temperatures when we climb a mountain. The temperature will drop by about 9.8°C for every 1 km of height. To make things easier, we'll refer to this as "Layer 1" or the "Urban Boundary Layer".​But the cold gradually fades. At a specific elevation, the temperature rises with altitude, known as "Layer 2" or "Inversion Layer". This layer is typically 1-2 km high but can be lower at times. After this level, the temperature will fall as the height rises, until we leave the earth's atmosphere. The "Inversion Layer" acts as a cone-shaped cover, preventing various particles from dispersing away from the "Urban Boundary Layer."​Depending on the height of the "Inversion Layer" above ground level, exhaust smoke from cars and particles from various sources will float higher and become diluted with the air. If it is higher, it will improve air ventilation by reducing pollution concentrations in the atmosphere. But if the "Inversion Layer" is low, air pollution will be concentrated and unable to float up or be diluted with air, resulting in inadequate air ventilation.​The height of the "Inversion Layer" depends on the time of day and season. During the day, when the sun's heat reaches the atmosphere, the air expands and rises. During the night, as the air cools to a high density, the "Inversion Layer" presses down and remains lower. During the winter, as air pressure rises, the "Urban Boundary Layer" is thinner than during the wet and hot seasons. As a result, many places experience higher PM2.5 concentration difficulties during the winter, both day and night, compared with other seasons.​Particle problems in many areas, particularly Bangkok, are caused by both human and natural forces during periods of inadequate ventilation. Understanding natural particle formation can help us create preventive technologies and manage specific human activities during periods of low natural ventilation, another critical issue for finding solutions and adapting to bad air quality.​Story by Dr. Parkin Maskulrath, Lecturer, Department of Environmental Science, Faculty of Environment, Kasetsart University and Thanawat Jinjaruk, Senior Researcher, Environment Division and Urban Environmental & Biodiversity Engineer, RISC​

Where Do PM2.5 Particles Come From?​

By RISC | 7 months ago

PM2.5 is a major issue in Bangkok every year. But do you know where the particles originate?More than 57% of PM2.5 particles in Bangkok come from automobiles (46% diesel cars and 11% gasoline cars), with 22% from construction, industry, and agriculture. The remaining 21% are secondary particles formed by gases such as sulfur dioxide (SO₂) and nitrogen dioxide. When these gases are exposed to sunlight and heat, they undergo a reaction that produces more PM2.5. ​The activities and environmental factors that cause PM2.5 occur primarily during the day. So why don’t PM2.5 levels drop at night? ​​A study of PM2.5 during days with no air fluctuations found concentrations were highest at night from 7 pm to 6 am. The morning hours from 6 am to noon will be more intense from noon to 7 pm in Bangkok and in other provincial areas. ​Meteorological conditions can be described using the ventilation flow rate (m²/s) based on wind speed (m/s) and atmospheric height (Planetary Boundary Layer (PBL) in meters. The PBL value represents the atmosphere near the earth's surface with turbulence due to the interaction of the ground and the lower atmosphere. Weather conditions with high PBL levels allow air to rise, lowering air pollution. If the weather has low PBL, the effect will be the opposite.​High PM2.5 at night comes from daytime activities that couldn’t vent air because of the rapid decrease in ventilation rates. ​PM2.5 density typically occurs from the night until the morning. During particle season, it is best to avoid exercising in the morning or late at night. Most importantly, before leaving the house each time, check the basic ventilation rate value from the Meteorological Department, which has a 7-day forecast, so you can deal with particles. ​Check the ventilation rate value from http://ozone.tmd.go.th/Daily_VR.html​Story by Napol Kieatkongmanee, Senior Sustainable Designer and TREES-A, Building Technology, Intelligent Systems, Innovative Solutions Specialist, RISC ​References:​Meteorological Department http://ozone.tmd.go.th/Daily_VR.html​http://164.115.28.46/thaiexen/file_upload/submitter/file_doc/108864782a2b951d956f1a72ffcf0dfeb22b1.pdf​Near-surface meteorological and air pollution measurement station Kasetsart University​

Love Is in the Air… and Dust Too Unless We’re Careful

By RISC | 8 months ago

February brings the festival of love when we give flowers or chocolates. But we should also look after the health of our loved ones by checking indoor air quality, an issue that’s often overlooked. ​​Did you know that the air we breathe indoors is 2-5 times more polluted than outside air? ​Air pollution, such as PM2.5, volatile organic compounds (VOC), and other allergens, is a silent, invisible menace constantly present in our homes. According to many studies, poor air quality can cause a variety of health problems, including coughing, sneezing, nasal congestion, respiratory and skin irritation, resulting in discomfort, decreased energy, difficulty sleeping, and an increased risk of serious diseases. PM2.5 has been linked to strokes and lung cancer. ​Indoor air quality affects both our physical and emotional wellness. According to one study, poor air quality can lead to weariness, headaches, and an increased risk of depression. ​Given these impacts, improving air quality is vital. Fortunately, it needn’t be difficult or expensive if we follow these tips.​• Open windows for ventilation: Even when PM2.5 levels are high, opening windows for ventilation is vital to decrease air pollution accumulation in buildings. Be aware of the best time to open windows and don’t leave them open for too long. At least two windows should be opened, either diagonally or facing each other. Using fans to ventilate the air will boost the flow of air throughout space. If you wish to make a small investment, install an air exchange system (Energy Recovery Ventilator: ERV) together with a particle filter.​• Clean your house to reduce pollutant accumulation: Activities and objects in the home can produce and accumulate air pollutants. Clean your home regularly with cleaning agents free from harsh chemicals. Clean your air conditioner and filter on a regular basis. If you have an air purifier, you should change the filter regularly.​• Choose the correct air purifier: An air purifier can help you manage various pollutants in your house, especially during the season when PM2.5 levels are high. There are several things to consider when choosing an air purifier, including room size, clean air generation rate (CADR: Clean Air Delivery Rate), and air filtering technology. Furthermore, the air filter efficiency should be HEPA H13 or higher to help filter PM2.5, with an activated carbon filter installed to remove VOC odors. Other considerations include loud noises, smart home connectivity, high-quality sensors, power consumption, warranties, and maintenance. Certified asthma & allergy friendly certification is required for air purifiers used by allergy sufferers. View the certified list at this link. https://www.asthmaandallergyfriendly.com/USA/products_categories/air-cleaners/​• Plant air-purifying trees: While trees are not as good at cleaning the air as air purifiers, they are another natural approach to help clean the air and can also benefit us in other ways, such as helping us feel relaxed and providing aesthetic value. Check out the list of air-purifying trees at https://risc.in.th/plants​• Check the outdoor and indoor air quality: Knowing air quality allows us to make better decisions about our lives. Depending on the air quality, you can open the windows and exercise outside or inside. Many websites and programs allow you to check the outdoor air quality. https://www.iqair.com/th-en/thailand/bangkok, https://aqicn.org/city/bangkok​If your air purifier already has a measuring sensor, you can check air quality with the color bar, screen, or application. You could buy a sensor with data on PM2.5, PM10, TVOC, and CO₂ concentrations.​When we improve indoor air quality, we see spectacular outcomes. In addition to minimizing respiratory difficulties, we may find that we have more energy, sleep better, and feel refreshed when we wake up in the morning without feeling irritation in our noses or respiratory systems. ​​Fresh air can make everyone in your home feel less stressed and happier. Having clean air indoors is another approach to foster love, happiness, and well-being. May each day be full of energy and enjoyment.​Story by Phetcharin Phongphetkul, Sustainable Designer/ LEED®AP BD+C, WELLTM AP,Fitwel Ambassador, ActiveScore AP, TREES-A NC, RISC ​References:​World Health Organization. (2021). Global Air Quality Guidelines: Particulate Matter (PM2.5 and PM10), Ozone, Nitrogen Dioxide, Sulfur Dioxide and Carbon Monoxide. https://www.who.int/publications/i/item/9789240034228  ​World Health Organization. (n.d.). Household air pollution and health. Retrieved from https://www.who.int/news-room/fact-sheets/detail/household-air-pollution-and-health?gclid=CjwKCAiAiP2tBhBXEiwACslfnsFOiv6qpy221c2deEtZKBJxcV7wYg0HuCAtETa_lJq7tKkAhp6NRxoC4DkQAvD_BwE  ​Allergy Standards Limited. (n.d.). Portable air cleaners. Retrieved from https://www.asthmaandallergyfriendly.com/USA/products_categories/air-cleaners/portable-air-cleaners/  ​IQAir. (n.d.). Air quality in Bangkok. Retrieved from https://www.iqair.com/th-en/thailand/bangkok  ​World Air Quality Index Project. (n.d.). Air quality information for Bangkok. Retrieved from https://aqicn.org/city/bangkok

Let's Change How We Burn Incense at Chinese New Year

By RISC | 8 months ago

Chinese New Year is a time to honor the gods and ancestors for success, luck, and wealth. In addition to sweet and savory dishes and fruits, a vital element is incense.​Incense sticks can be used to make offering to the spirit of a house and to present food. The smoke should help the prayer or message reach its intended receiver.But we’re also inhaling harmful substances such as small particulate matter (PM), which is 4.5 times higher than in cigarette smoke, as well as carbon monoxide (CO), carbon dioxide (CO₂), sulfur dioxide (SO₂), nitrogen dioxide (NO₂), volatile organic compounds (VOCs), and polycyclic aromatic hydrocarbons (PAHs), which are air pollutants and harmful to our bodies. These compounds can cause respiratory problems, allergies, dermatitis, and cancer.​Incense also pollutes the environment by emitting carbon dioxide, a greenhouse gas that contributes significantly to global warming. Incense sticks emits carbon dioxide equal to a third of their weight. The more incense burnt, the bigger the environmental impact.​During this Chinese New Year, let's try a new method: put out the incense stick before placing it in the pot. Don't let it burn until it goes out on its own. We can also use electronic incense sticks that don’t require combustion to protect the health of ourselves, our families, and those around us, as well as to look after the planet.​Story by: Supunnapang Raksawong, Materials Researcher in Sustainable Building Material, RISC ​References:​1. Krishnaswamy G, Chi DS. Incense smoke: clinical, structural and molecular effects on airway disease. Clin Mol Allergy. 2008 Apr 25;6:3.​2.https://www.mnre.go.th/attachment/iu/download.php?WP=rUIjnJ0jqmMZZJ1CM5O0hJatrTgjWz0kqmMZAJ1CM5O0hJatrTDo7o3Q

For High PM2.5, an Air-Filtering System Isn’t Enough

By RISC | 9 months ago

Did you know that staying indoors when air pollution is high doesn’t protect you?​Our homes or workplaces can’t completely shield us from PM2.5 or smaller particles. These particles are small enough to pass through closed doorways or windows. Air purifiers can, to some extent, capture PM2.5. But the particles can continue to enter the building through various openings.​So how do we deal with this problem?​One way is to increase the air pressure inside the building to create a positive pressure environment. Higher air pressure will push out air containing PM2.5 and other particles.​A positive pressure system can be used with an outside intake and an air filter capable of filtering small particles (HEPA H13 Filter). The following conditions are need for a positive pressure air condition:​• Supply air: With minimum ventilation rates and standards. Residential buildings, for example, require an air change rate of 0.35-1 ACH (but not less than 15 cfm/person), with bedrooms recommended at 2-4 ACH and living rooms recommended at 3-6 ACH in case of co-infection prevention.​• Exhaust air: The exhaust air volume must be 10-15% less than the supply air volume.​• The difference in air pressure inside and outside the building must be greater than 2.5 Pa (a difference of 8 Pa is considered completely positive air pressure that can protect against particles).​Aerating and maintaining positive pressure in buildings will have no effect on us. It also aids in the reduction of carbon dioxide produced by breathing in the room.​We may not be able to avoid the particle season today. Our home is our last line of defense. If the ventilation system is properly designed, it will allow us to stay in the house safely. If you go outside, remember to wear a mask to protect yourself from PM2.5.​Story by: Napol Kieatkongmanee, Senior Sustainable Designer and TREES-A, Building Technology, Intelligent Systems, Innovative Solutions Specialist, RISC​References:​https://acat.or.th/download/acat_or_th/V26-(2).pdf​https://commercialairfiltration.co.uk/blogs/news/positive-and-negative-pressure-rooms#:~:text=Air%20pressure%20in%20the%20room,ideally%20should%20be%208%20Pa.​https://www.tmn.co.th/download/tmn_co_th/CL_Cooling_Load_Calc/Calculations-of-Ventilation-Rate-According-to-ASHRAE-Standard-62-1.pdf​

How to Choose an Air Filter by Particle Size?​

By RISC | 11 months ago

The PM2.5 problem remains a chronic issue since the causes—vehicle exhaust, industrial pollution, agricultural burn-off, including from neighboring countries—have not yet been solved. Particles in the air reach unhealthy levels during the winter with still weather and calm wind.​If you have to go outside, wear a mask. Also, in accordance with US National Institute for Occupational Safety and Health (NIOSH) guidelines, masks help protect against PM2.5 particles (dust no bigger than 2.5 microns). A N95 mask is named with N for non-oil-resistant and can filter at least 95% of particles less than 0.3 microns.​But are we safe inside with air conditioning and closed doors and windows?​It depends on building leaks. But the more closed a building is, the more likely that it will accumulative pollutants, such as CO2 from breathing or volatile organic compounds (VOCs) from household cleaning products, perfumes, furniture, or building materials. If these pollutants rise above standard levels, the health of the residents may suffer.​A Fresh Air Unit (FAU) system, Outdoor Air Unit (OAU), or Energy Recovery Ventilator (ERV) can help deal with PM2.5 indoors. To prevent PM2.5 from entering the building, the system exchanges indoor air pollutants and filters outdoor air before bringing it in.​There are many different types of air filters available depending on the type of pollution. There are several different standards for particle filters based on their properties and filtration efficiency per particle size. The ASHRAE 52.2-1999 standard is referred to by some manufacturers. The American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE) is an American air conditioning and refrigeration engineering society that categorizes filtering levels into MERV (Minimum Efficiency Reporting Value) levels ranging from MERV1 to MERV16.​Choose an air filter with a MERV 13 or higher to filter PM2.5 particles or particles smaller than 2.5 microns. The ability to filter will improve as the MERV increases.​ Furthermore, some manufacturers may refer to the EN779:2012 standard, which is a 2012 revision of the European Standard. Air filters are classified as coarse or fine filters under European standards. The weight of the particles that the air filter can hold is used to classify the G1-G4 grade filters or coarse filters. The efficiency of fine filters in grades M5-F9 in filtering particles with a diameter of 0.4 microns is measured. In comparison to MERV values of 13 or higher for PM2.5 filtering, choose a filter at level F7 or higher from the table below.​ Since we know the level of particle filtration, we can select and purchase appropriate air filters to ensure the good health of building occupants.​Story by Panpisu Julpanwattana, Senior Sustainable Designer and TREES-A Specialist, RISC