Last autumn I wrote a very popular piece covering my escapades around town with an air particle monitor. I had so much fun that I borrowed the monitor again last winter and published my findings in CityWeekend Beijing Parents & Kids magazine, now published every two months. Here is my reprint:

Winter this year started early, and so did the seasonal decrease in air quality, traditionally due to home coal burning and weather patterns. As we are now snuggled away indoors, this is the perfect time to review how indoor air quality can also affect the health of you and your family. Some indoor chemicals such as formaldehyde and benzene are well known hazards, but probably the biggest indoor worry in Beijing is the same outdoor air pollution that easily seeps indoors. Many schools monitor outdoor air quality data for their pollution alert systems, but is their indoor air safe enough? And what about other buildings, such as your home or office, or malls, restaurants and hotels? How is their air quality, and what can we do to minimize indoor pollution’s effects?

To assess these issues, I borrowed a ParticleScan Pro portable monitor from the IQAir air purifier company for one week, and I took dozens of readings from multiple indoor and outdoor spots. I measured tiny particles 0.3 microns in size, which the World Health Organization considers the most dangerous to your health — especially for young children, the elderly, and those with heart and lung diseases. These particulates are created mostly by coal burning, factories and vehicle exhaust, especially diesel.

The scanner uses a laser to tally the number of particles per liter of air. The IQAir guidelines recommend indoor air readings under 100,000 as safest, and anything over 300,000 as hazardous. For simplicity in this article, we will lop off 3 zeroes (i.e. anything over 300 is hazardous). Please note that this number cannot be directly compared to other official pollution indexes as the technique and particle sizes are different.

Major findings:

One finding common to all places was that indoor air quality is strongly related to the outdoor air, and open windows and doors, as well as leaks around them, can quickly cause indoor air quality to rise and fall with outdoor air levels. I also noticed that on the worst outdoor days when levels were over 600, the indoor air in all places, while lower than outside, was still at unhealthy levels over 300. That’s because those pollution particulates are so small, they simply diffuse rapidly and easily into buildings. In general, most buildings’ indoor air was 40%-80% better than outdoors. For example, on December 7th the outdoor air was 1140, and indoor air in my office was 750; a mall was 920; and home was 380. (Don’t forget that readings 300 and above are unhealthy).

Malls, Offices, Restaurants:

One enclosed mall had a level of 920 with outdoor air at 1500. Another open-air mall had readings 1150-1490, with outside air 1560. One very popular expat bookstore/cafe had indoor levels even higher than the already hazardous outdoor levels, which was quite rare. Their indoor air smoking section was 1720, and non-smoking room was 1600, and outside was 1320. This seemed due to a lack of proper ventilation as well as their smoking section, which easily permeated into their non-smoking rooms. Most indoor malls and offices had levels 50-90% of the outside air, depending on how well sealed and ventilated they were. Again, many times the indoor air was far above healthy levels, and was always related to the outdoor air levels.

Gyms:

The gyms I sampled did well, usually about half the levels of outdoor air. One gym had a level of 65, with outdoor air 120. That healthy level probably was due to their good HVAC systems and filters. But each gym is different, so it’s good to ask your gym what they do to keep their air quality healthy.

Home:

My home, after weatherproofing some drafty windows, had levels 70% of outdoor air with no air purifiers. After cranking up both of my imported air purifiers to the max for two hours, I dramatically improved the ratio to 9-21% (indoor levels 140-320, outside 1500). On a usual day when my air purifiers are at a quieter middle setting, the indoor air was 20-40% better than outside. For example, on a good day with outdoor air 200, my indoor air was 60. Usually, outdoor air — and therefore, indoor air — is worst overnight due to diesel trucks and construction sites. So, I feel more comfortable keeping my windows closed with my bedroom air purifier set at a higher level, yet still quiet enough for sleep. One benefit of these new air quality websites (iphone.bjair.info) is that I will check the current Air Quality Index (AQI), and if it is high I will turn up my purifiers a level or two.

What about smoking?

 

I did a few samples from smoky restaurants and bars and found all samples in smoking areas far above the safety threshold of 300. My highest recording anywhere, at 1720, was in a bookstore cafe smoking section. A five-star hotel’s lobby lounge had a level of 1126, much higher than the outdoor air at 720. All readings were at levels hazardous to health, and it’s crucial for these places to have proper ventilation and air filters. The long-term effects of indoor smoking are a well-documented health risk to their full time staff, not to mention the short-term risks to their customers. The ideal option, of course, is to ban indoor smoking entirely, as I found all non-smoking sections entirely ineffective in improving the air quality in any meaningful way. Let’s say that again:

The ideal option, of course, is to ban indoor smoking entirely, as I found all non-smoking sections entirely ineffective in improving the air quality in any meaningful way.

What can you do?

• All owners of indoor spaces should periodically reevaluate and update their weatherproofing and air filters and purifiers. I bought weatherproofing strips (menchuang mifeng jiaotiao 门窗密封胶条) at B&Q for 35RMB a box, and instantly noticed a 10% improvement in indoor air particle numbers, not to mention the gains in heating and AC efficiency.
• Air filters and purifiers also play a key role, especially on the worst outside days.
• Large buildings, homes and schools should ensure that their HVAC ventilation systems use filters with a minimum efficiency rating value (MERV) of 13 or above, and replace them at the proper intervals. Stand-alone air purifiers can be placed in poorly ventilated areas or places with the most vulnerable people (preschool rooms, bedrooms).
• Children are most at risk of pollution’s ill effects, so schools should be especially vigilant in monitoring real-time pollution data via websites and implementing action plans as needed. For example, a reported AQI higher than 200 may call for postponing all outdoor PE and sports.
• Also, we should all encourage non-smoking in all indoor areas, especially your own home.

 

The Bottom Line:

We all spend 80-90% of our time indoors, especially in winter, so it’s important to be proactive and take control over our indoor air quality. Even while indoors, fine particulate pollution levels can be high enough to cause both short-term and long-term health effects, especially for small children. Fortunately, with a bit of indoor maintenance and monitoring websites such as iphone.bjair.info, you can dramatically reduce those risks.

UPDATE 2024: Please follow me at my new website, DrSaintCyr.com. Also my new YouTube channel youtube.com/@drsaintcyr