The Complete Guide to Air Pollution in Bangkok: PM2.5, Air Purifiers, Masks, and More

This guide covers air pollution in Bangkok from the ground up: what PM2.5 is, when the smog season peaks, how to check the air quality each day, and the masks, air purifiers, and habits that lower your exposure.

I’m sure you’ve heard it. The pollution in Bangkok can be bad. Really bad.

So bad, in fact, that the government is thinking about seeding the clouds to make it rain and knock down some of the pollution floating around.

I don’t know about you, but this worries me. Especially since I have two young kids.

My wife and I have been finding out ways to limit our exposure to the pollution, or PM2.5.

What is this PM2.5 that everyone’s talking about anyway?

I thought I’d share our tips and resources with you so that you can better protect yourself and your family.

Disclaimer: Some links in this article go to our partners, and we may earn a commission if you use them. It costs you nothing extra, and we only recommend services we'd use ourselves. Read more in our Advertising Disclosure.

What is PM2.5?

PM2.5 is any particle in the air that measures less than 2.5 microns. So the pollution itself isn’t PM2.5, it’s the size of the pollution that’s referred to as PM2.5.

Thailand’s national PM2.5 standard is 37.5 micrograms per cubic metre for a 24-hour average and 15 for an annual average. The WHO 2021 guideline is stricter, at 15 for a 24-hour average and 5 for an annual average.

You need to worry about this because this is the size of pollution that can get past nose hairs, into the lungs, and possibly into the circulatory system.

The particles are so small that about 40 of them can fit around the diameter of one human hair.

If you want a more scientific explanation of PM2.5, check out this article.

When Does It Happen?

Air pollution is likely to be a regular event in Bangkok from roughly December to April, with the worst weeks usually January to March.

During this season, there’s a change in air pressure in the entire country. This results in less wind to blow away air pollution caused by cars, construction, and factories.

In the end, the pollution gets locked up in many parts of Thailand and creates health problems until the summer, when the wind starts blowing again.

During this season, the price of masks and air purifiers is expected to significantly increase.

During the air pollution period, you may need to pay a premium to get an air purifier and wait for more than 2 weeks for it to ship.

In case you don’t have one yet, it’s better to stock up on air purifiers, filters, and masks before the air pollution hits Bangkok again.

Where PM2.5 Comes From

PM2.5 comes from many sources in and around Bangkok, The worst spikes are driven largely by regional and transboundary agricultural burning, on top of year-round traffic and industry.

Some experts believe the pollution is mostly from the following:

Advertisement

Agriculture and Industry

Thailand is still a slash-and-burn society. Each year during the cold season, farmers burn their fields to destroy weeds and prepare for the seeding season.

Air pollution also comes from factories and power plants.

Although pollution from field burning, factories, and power plants doesn’t happen in Bangkok, air currents blow pollutants from surrounding provinces into Bangkok.

Construction

Bangkok is expanding the BTS and MRT lines all over the city. With all the construction going on, it’s putting a lot of particles in the air.

Traffic

Bangkok is known for its heavy traffic. With construction happening all over the place, narrowing roads and detours cause gridlock, and cars release more CO2 into the air.

Old Vehicles

A majority of buses in Bangkok have been in operation for over 20 years. The engines are no longer in good condition and release smog everywhere they go.

And this smog doesn’t only come from buses, but also from construction trucks, cars, and tuk-tuks.

Dangers of PM2.5

If you’re exposed to PM2.5 for long periods of time, you could wind up with a list of premature health concerns ranging from asthma to cancer and everything in between. This is one reason why having health insurance in Thailand is highly recommended.

The unfortunate part about this is that “long-term exposure” isn’t really defined. Reports define long-term exposure as anywhere from months to years.

But here’s what Dr. Gerard Lalande, author of Stay Healthy in the Asian Tropics and Chief Medical Officer of Luma Health, said when we asked for his input on 2.5PM exposure time:

If you ever need to visit private hospitals in Bangkok for respiratory issues, doctors will highlight these concerns.

Here are some of the health risks you can face if exposed to PM2.5. The AQI is an index, not the amount of PM2.5 itself. The table below uses the US-style scale that many apps show. Thailand’s own scale, used by Air4Thai, is explained further down.

I show you how to find the levels of PM2.5 in your area in the How Polluted is Your Area? section.

AQI Level	Health Descriptor	Meaning
0 – 50	Good	Satisfactory-little or no risk
51 – 100	Moderate	Acceptable-health concerns for sensitive people
101 – 150	Unhealthy for Sensitive Groups	Dangerous to children and adults with lung disease or other respiratory issues
151 – 200	Unhealthy	Dangerous to everyone
201 – 300	Very Unhealthy	Dangerous to everyone with noticeable health effects
301 – 500	Hazardous	Emergency conditions-everyone will be affected

Thailand’s Official PM2.5 Limit and AQI Colours

Thailand’s Pollution Control Department (PCD) sets the national limit. Since 1 June 2023, the 24-hour average for PM2.5 must not exceed 37.5 micrograms per cubic metre, down from 50. The one-year average limit was cut from 25 to 15. (Verified October 2026.)

The PCD also rewrote its Air Quality Index to match the new limits. On this scale an AQI of 100 equals the national standard, so any reading above 100 means PM2.5 is over the legal limit. Air4Thai uses this scale, with five colours.

Colour	Air4Thai AQI	PM2.5 (µg/m³)	Level	What the PCD advises
Blue	0 to 25	0 to 15	Very good	Everyone can carry on as normal.
Green	26 to 50	15 to 25	Good	Normal outdoor activity. People in at-risk groups should watch for coughing, breathlessness or chest tightness.
Yellow	51 to 100	25.1 to 37.5	Moderate	Everyone: cut back on hard outdoor exercise. At-risk groups: wear a PM2.5 mask every time you go outside.
Orange	101 to 200	37.6 to 75	Starting to affect health	Everyone: wear a PM2.5 mask outdoors and limit hard exercise outside. At-risk groups: avoid hard outdoor activity.
Red	201 and above	75.1 and above	Affects health	Everyone: skip outdoor activities, or wear a PM2.5 mask if you cannot. People with health conditions should stay somewhere clean and keep medicine ready.

This is Thailand’s own scale. Apps that use another country’s scale can show a different AQI number for the same PM2.5 reading, so compare the micrograms per cubic metre figure when two sources disagree.

Checking Air Quality in Bangkok

You may not know it, but you could be living in one of the most polluted spots of Bangkok. But there are a few easy ways to check your area:

• Websites
• Apps
• Monitors

Air Quality Index Websites

Below are two air quality index websites that you can use to check the quality of air in Bangkok, alongside the government’s own Air4Thai. It’s best not to rely on one single source, so check more than one to be sure of their accuracy.

Aqicn.org

Aqicn.org gathers air quality data from five different sources to calculate the amount of PM2.5 in Bangkok’s air. They also give a seven-day air quality forecast based on previous data.

IQAir AirVisual

IQAir AirVisual gathers their air quality data from 15 different sources to calculate the amount of PM2.5 in Bangkok’s air.

They also offer a wide range of other data, including hourly PM2.5 forecasts, historical data, and seven-day forecasts.

You can even select a location closest to you to get the most accurate readings.

Air Quality Index and Visual Apps

If you have to go outside, leave your house when the air quality is at its best. This way you can see what the air quality is like where you live and plan your trips outside accordingly.

IQAir AirVisual App

IQAir AirVisual (mentioned above) has an app for iOS or Android. It’s a handy app that lets you select the nearest location to you and gives you up-to-the-second updates on the air quality in your area.

As you can see from my screenshot, we’ve been living in one of the unhealthiest areas. The scary part is that we weren’t even aware of this until we downloaded the app.

We’re now starting to wonder if this has led to my youngest daughter’s allergies, and it’s why we’re moving in March.

Air4Thai

Air4Thai is another app for iOS and Android that gives you up-to-second updates on the air quality in your area, but it doesn’t use any outside sources to help them gather their info.

Air4Thai shows very low readings compared to IQAir AirVisual, which has led to concern for some Thai netizens. Air4Thai reports from government monitoring stations, while IQAir blends several data sources, so the two can differ.

Air Quality Monitors

If you want to monitor your house for PM2.5, or take a monitor on the go in your car. If you don’t mind the brand, you can buy a PM2.5 monitor online online as budget to mid-range options are widely available.

Here are a few monitors that could help you.

Smart Air Quality Monitors

Smart Air has a portable PM2.5 monitor. It can track PM2.5, PM10, CO2, temperature, and humidity. The Smart Air Monitor can be recharged with a USB-C and can connect to the Apple Home or Xiaomi App.

IQAirVisual

The IQAirVisual monitor goes hand-in-hand with their app and website. In fact, when you get one of their monitors, you can opt to send results to their website, so that people in your area can see the PM2.5 levels as well.

This monitor will cost you around a premium option and is not cheap.

Other

Lazada has a list of PM2.5 monitors for sale, but the lack of reviews makes buying one a roll of the dice. Budget to mid-range options are widely available.

What Bangkok Does When PM2.5 Spikes

The Bangkok Metropolitan Administration (BMA) runs its own alerts and rules on top of the PCD’s national readings. These are the ones that affect daily life. (Verified October 2026.)

• Readings and alerts: The BMA’s Greener Bangkok site posts daily PM2.5 levels and points residents to the AirBKK and Air4Thai apps. It also offers a LINE alert that fires when PM2.5 passes the standard.
• Work from home network: Companies can register with the BMA. When PM2.5 stays above 75 µg/m³ for three days in a row, the BMA alerts registered companies, which can then send staff home for the number of days they signed up for. It is a voluntary scheme, not an order.
• School closures: Under a guideline the BMA announced in January 2025, a school director can close a BMA school for up to 3 days during red readings, and a district director for up to 7 days. If red readings last more than 3 days across five districts, the head of the BMA Education Department can close schools for up to 15 days. Across more than five districts, the governor can close them with no time limit.
• Who the school rules cover: They apply to schools run by the BMA. The governor has said the BMA has no authority over schools run by the Ministry of Education or private schools, so ask your own school how it handles red days.

Readings also differ from district to district. If you are still choosing where to live, our guide to living in the Bangkok suburbs is a good place to compare areas before you check their air.

Advertisement

How to Protect Yourself Outside

Now that you know what PM2.5 is, where it comes from, and the dangers of being exposed to it, let’s look at how to protect yourself from it.

You can’t just barricade your family indoors. So here are a few things you can do to limit your exposure to pollution outdoors.

Masks

You might feel like you’re living in End of Days, but wearing the proper mask will reduce the amount of pollution that enters your lungs.

To find out why KN95 masks are important, or which masks you can use in their place, read this article by the World Air Quality Index.

But in order to work, masks must fit tightly and be rated to filter PM2.5.

A plain surgical mask only stops larger dust and does very little against PM2.5. It doesn’t fit snugly around your face, so you breathe in unfiltered air through the gaps. Use a KN95 or N95 mask if you can.

3M FFP3 Masks

When it comes to masks that filter out PM2.5, 3M 9332 masks are always a top-performing option.

I haven’t seen these masks for sale in Bangkok. But you can order them on Lazada.

3M KN95 Masks

Your next best option is the 3M KN95 masks. You can find these at 7-11 or Tops Market. They come in a blue and white box. A well-fitted N95 or KN95 respirator filters PM2.5 effectively.

You need masks like 3M’s KN95 mask or equivalent. You can buy KN95 masks online. But when pollution is at its worst, they sell out quickly.

Surgical Masks

If you can’t find masks rated to filter PM2.5, you can use surgical masks. But surgical masks won’t filter as much PM2.5 because they don’t fit snugly around your face.

A loose surgical or cloth mask does not seal to the face and offers far less protection, so fit matters as much as the rating. In a bind, surgical masks are better than nothing.

Surgical masks rarely sell out. You can find them at any convenience store or pharmacy in Thailand.

It’s best to stock up on 3M masks so that you have them when you need them. Or you can order them online. My wife just found some 3M masks on Lazada and had them delivered within 24 hours.

How to Protect Yourself Inside

We can’t control everything that’s happening outside of our homes, but we can control what’s happening inside.

Here are a few ways to reduce the amount of pollution getting in your home.

Invest in Air Purifiers

When it comes to air purifiers, don’t buy anything other than a HEPA air purifier.

Other systems may claim to be better, but research shows that HEPA systems are the absolute best for removing pollution particles from the air.

Although expensive, HEPA air purifiers can significantly reduce the amount of pollution in your home. And you don’t even need a top-of-the-line purifier.

Air Purifier Reviews

We have a separate article on how to choose a good air purifier in Thailand.

Another popular air purifier you can get in Thailand is from Xiaomi. You can order it from Lazada. It usually takes just a few days to deliver.

Note that the cost of air purifiers and masks tends to significantly increase when Bangkok has an air pollution problem.

The increase was considerably from the normal rate in the last few years. And sometimes, they’re out of stock.

So if you plan to live here, it’s better to get one yourself before the price increases.

If you’re looking for a general overview of air purifiers on the market, and you don’t mind shipping to Thailand, you can check out WireCutter’s review of air purifiers.

You might not be able to buy some of the air purifiers on their list, but you’ll know which specs they used to review each one, and then be able to look for those specs on air purifiers in Thailand.

Where to Buy

In Bangkok, you can buy air purifiers on- or offline. Some places may offer a better selection than others. So be sure to check around.

Lazada

Lazada sells a variety of air purifiers as well. But they tend to sell out when pollution gets really bad in Bangkok.

Home Pro

If you’re looking for a one-stop place to pick up a purifier, check out Home Pro’s selection of air purifiers. They carry a variety of air purifiers for all budgets. One downside is that those are probably the first ones to sell out when pollution hits, so be sure to call ahead to check if the shop has any in stock.

Central

Central Mall is the official retailer of Blue Air Purifiers in Thailand. Blue Air is one of the most recommended brands according to WireCutter. You can buy air purifiers through Central’s online shop. Central though is definitely on the pricier side of things when it comes to air purifiers.

Sizing Air Purifiers

The size of the air purifier you need depends on the size and layout of your living space.

If you live in an open floor plan, you can get away with buying one large air purifier. But if you live in a space with many closed-off rooms, you need to buy smaller air purifiers for each room.

In order to get the right-sized purifier, you need to calculate the square footage of the space you intend to keep the purifier in. Then you’ll compare that number to the rating on the purifier.

The general rule of thumb is to buy an air purifier rated for 20% larger than the space you need to purify.

So if your studio apartment is 75 square meters, you’d need an air purifier rated for 90 square meters.

If you buy an air purifier that is slightly oversized, your purifier won’t run as much, saving you costs on electricity.

DIY Air Purifiers

Some people have made purifiers using fans and HEPA filters that have worked just as well as brand-name purifiers.

If you search DIY HEPA air purifiers on YouTube, a list of videos will come up.

Although the guy in this video is selling these homemade HEPA air purifiers, you can get HEPA filters and floor fans, the two materials needed, at Home Pro or Thai Watsadu.

Close Windows and Doors

You might like to open the doors and windows early in the morning to clear the stagnant air out of your home or enjoy the crossbreeze instead of kicking on the ac.

But by doing this, you’re letting pollution into your living space.

It’s best to keep all windows and doors closed when PM2.5 readings are at unhealthy levels.

Keep Plants

Neither my wife nor I have green thumbs. Most plants we buy, die. But after I came across this TED talk about how to create clean air in your home, I thought I’d give plants another shot.

The three plants mentioned in the short video are:

• Areca Palm
• Mother-in-Law’s Tongue
• Money Plant

These plants are all available at local Thai garden centers. They help filter the air and they produce oxygen.

But you have to buy them according to how many people are in your home. So watch this four-minute video and take notes to get the full benefits of these plants.

Masks and Dust-Free Rooms: What Thai Health Authorities Say

The Department of Health and the BMA publish practical advice on masks and home air. It matches the mask and purifier tips above and adds a few details worth following. (Verified October 2026.)

Check the Fit of Your Mask

A BMA health centre notes that an ordinary medical mask only stops larger dust. Look for a mask marked KN95 or N95, or one that says it filters PM2.5. Then test the fit using the Department of Health’s steps:

1. Wash your hands before you put the mask on.
2. Choose a mask with two straps that covers your nose and chin snugly, and do not wear one that is bent or folded.
3. Put one strap above your ears and the other below them, then pull both tight.
4. Press the metal strip firmly onto the bridge of your nose.
5. Cup both hands around the mask and breathe out harder than normal. If no air leaks out around the edges, the fit is good.

For exercise, the BMA says never to wear an N95 mask while working out, and to avoid outdoor exercise when readings are red. Exercise in a park where trees help filter dust, and cut back when readings are orange.

Set Up a Dust-Free Room

Both the Department of Health and the BMA recommend one sealed room for orange and red days, especially when young children live in the home. Their advice covers these points:

• Wipe surfaces with a damp cloth every day. Do not use a broom or vacuum, which throw dust back into the air.
• Seal gaps and keep doors and windows shut. Open them only when outdoor dust is low.
• Skip incense, candles and anything else that makes smoke indoors.
• Clean the air-conditioner filter every month, and add an air purifier to cut dust further.

How About Other Provinces

Other provinces also have air pollution problems from roughly December to April, with the worst weeks usually January to March. But it was not as bad as in Bangkok, except for some provinces in the north, including Chiang Mai and Chiang Rai.

In Chiang Mai, the air quality level during the cold season can be worse than in Bangkok. People often wonder is Chiang Mai safe to visit during this time. The worst part is that it lasts until April.

The air pollution problem is worse in provinces like Chon Buri, Samut Prakan, and Samut Sakhon where there are many factories.

The good news for those who live in the beach destinations in the Southern Part of Thailand, including Suratthani, Hua Hin, and Phuket, is that you are unlikely to be affected by the air pollution. It is always windy there.

Frequently Asked Questions

Is Bangkok’s air pollution really that bad?

For much of the year the air is acceptable, but during the dry-season peak Bangkok’s PM2.5 regularly exceeds both Thailand’s and the WHO’s health guidelines. The problem is seasonal rather than constant.

When is Bangkok’s pollution season?

Roughly December to April, with the worst weeks usually January to March, when dry weather and regional crop burning combine. Air quality is generally much better during the rainy season.

What is PM2.5 and why does it matter?

PM2.5 is fine particulate matter 2.5 microns across or smaller, small enough to reach deep into the lungs and enter the bloodstream. Thailand’s 24-hour standard is 37.5 micrograms per cubic metre; the WHO guideline is stricter at 15.

Where does Bangkok’s PM2.5 come from?

The worst spikes are driven largely by regional and transboundary agricultural burning, on top of year-round traffic and industry. That is why the peaks line up with the dry burning season rather than being constant.

How do I check the air quality in Bangkok right now?

Check the Pollution Control Department’s Air4Thai service, or apps such as AQICN or IQAir, which report a live AQI and PM2.5 reading by area. Check before outdoor exercise during the season.

Is it safe to live in Bangkok given the pollution?

Many people live in Bangkok long-term and manage the season with an air purifier indoors and a mask outdoors on bad days. People with asthma, heart conditions, young children, or elderly family members should take the peak weeks more seriously.

What is the best mask for PM2.5 in Bangkok?

A well-fitted N95 or KN95 respirator filters PM2.5 effectively. A loose surgical or cloth mask does not seal to the face and offers far less protection, so fit matters as much as the rating.

Do air purifiers actually help indoors?

Yes. A purifier with a true HEPA filter, sized to the room, measurably lowers indoor PM2.5. Keep windows closed on bad days and run it in the rooms where you spend the most time.

What do the Air4Thai colours mean?

Blue is very good air, green is good, yellow is moderate, orange means air that is starting to affect health, and red means air that affects health. Orange begins at a PM2.5 reading of 37.6 µg/m³ and red at 75.1, according to the Pollution Control Department. Yellow and above is the point where people in at-risk groups should wear a PM2.5 mask outdoors.

Why does Air4Thai show a different AQI from my air quality app?

Air4Thai uses Thailand’s own AQI scale, where 100 equals the national PM2.5 standard of 37.5 µg/m³. Apps built on another country’s scale can show a different number for the same air. Compare the PM2.5 reading in micrograms per cubic metre to see whether the sources really disagree.

Does Bangkok close schools or send workers home when PM2.5 is high?

It can for BMA-run schools. Under the BMA’s January 2025 guideline, school directors, district directors, the Education Department and the governor can close schools in stages as red readings persist. Offices are not ordered home. The BMA’s work-from-home network alerts registered companies when PM2.5 stays above 75 µg/m³ for three days, and each company decides. Schools run by the Ministry of Education or privately are outside the BMA’s authority.

At what PM2.5 level should I wear a mask?

The PCD advises people in at-risk groups to wear a PM2.5 mask outdoors from the yellow level (25.1 to 37.5 µg/m³). Everyone is advised to wear one from orange (37.6 to 75). On red days it recommends skipping outdoor activity and wearing a mask if you have to go out.

Can I wear an N95 mask while exercising outdoors?

The BMA advises against it, saying never to wear an N95 mask while exercising. Check Air4Thai or the AirBKK app first, exercise in a park, and avoid outdoor exercise on red days. When readings are orange, cut back or move the workout indoors.

Sources Cited

• Pollution Control Department / Air4Thai
• World Health Organization air-quality guidelines
• US EPA (HEPA definition)
• NIOSH (N95 standard)
• Pollution Control Department: new PM2.5 standard in force from 1 June 2023: the 37.5 µg/m³ 24-hour limit (down from 50) and 15 µg/m³ annual limit (down from 25).
• Pollution Control Department: Thailand’s Air Quality Index 2023: the five AQI colours, PM2.5 bands and health advice, published in the Royal Gazette on 3 July 2023.
• Bangkok Metropolitan Administration: PM2.5 self-care guide: AirBKK and Air4Thai apps, LINE alert, exercise and N95 advice, dust-free room tips.
• Bangkok Metropolitan Administration: Work From Home network: the 75 µg/m³ for three days alert rule for registered companies.
• Public Relations Department: BMA school closure guideline, January 2025: who can close BMA schools and for how long.
• Department of Health: wearing a PM2.5 mask correctly: mask fit steps.
• Department of Health: dust-free room: damp-cloth cleaning, avoiding smoke sources, monthly air-conditioner filter cleaning.

Now, on to You

No matter which steps you take, be sure to protect yourself and your family. If you are wondering is Bangkok safe overall, taking steps to handle the air quality makes a huge difference. No one is sure how long this pollution in Bangkok is going to last, but let this guide be the beginning to your pollution preparation.

To prepare yourself, it’s better to invest in an air purifier. You will need it.

If I’ve forgotten to add any resources, or if you have any tips or techniques to stay healthy from the pollution in Bangkok, share your advice with our community in the comments section below.

Featured image courtesy of Scotty_. Other images courtesy of octal, danebrian, 71267357@N06, and noshit-mag.