Bedroom Air Quality

In this article, I describe common issues with air quality in unventilated bedrooms. Also, I suggest potential solutions for these issues.

Issues

Carbon Dioxide Levels

What are Acceptable CO2 Levels?

Between 1000ppm and 1500ppm.

Carbon dioxide limit for acceptable indoor air quality: 1000ppm (average over 8 hours)

NEA Office Indoor Air Quality Guidelines

Carbon dioxide acceptable limit: 700ppm above outdoor (average over 8 hours)

Singapore Standards 554 2009

Note that outdoor CO2 levels average from 400-500ppm.

What are Typical Levels in Unventilated Bedrooms?

Before I get into this, we must first take a closer look at the ppm unit. ppm stands for parts per million. It's a measure for concentration. For example, if the CO2 level in a room is 1000ppm and the room's volume is 1000000L, then the room contains 1000L of CO2.

A person exhales about 19L of CO2 per hour:

A conservative estimate based on a person who spends eight hours a day sleeping and 16 hours in normal activities, but one who does not add to the atmospheric burden by exercise, would thus come to about 456 liters of carbon dioxide a day

Q&A; Burden of Breathing, by the New York Times.

The volume of a typical HDB room is 36000L. Thus:

19/36000 x 1000000 ≈ 528

CO2 levels can increase by around 528ppm per hour. There are variables this calculation does not consider. For example, exchange of indoor and outdoor air through gaps. However, the result is consistent with my measurements. Using a CO2 meter, I found CO2 levels in my room rose to ~2000ppm within 2 hours.

What are the Consequence of High CO2 Levels?

Here's a broad overview:

350 - 1,000 ppm: typical level found in occupied spaces with good air exchange.
1,000 - 2,000 ppm: level associated with complaints of drowsiness and poor air.
2,000 - 5,000 ppm: level associated with headaches, sleepiness, and stagnant, stale, stuffy air. Poor concentration, loss of attention, increased heart rate and slight nausea may also be present.

Carbon Dioxide, by the Wisconsin Department of Health Services.

Studies have been conducted on specific consequences:

Objectively measured sleep quality and the perceived freshness of bedroom air improved significantly when the CO2 level was lower, as did next-day reported sleepiness and ability to concentrate and the subjects' performance of a test of logical thinking.

The effects of bedroom air quality on sleep and next-day performance, by Strøm-Tejsen, Technical University of Denmark.

Cognitive function scores were significantly better under Green+ (high outdoor ventilation rate) building conditions than in the Conventional building conditions for all nine functional domains. These findings have wide-ranging implications because this study was designed to reflect conditions that are commonly encountered every day in many indoor environments.

Associations of Cognitive Function Scores with Carbon Dioxide, Ventilation, and Volatile Organic Compound Exposures in Office Workers: A Controlled Exposure Study of Green and Conventional Office Environments, by Joseph G. Allen, Harvard T.H. Chan School of Public Health.

Analysis of the OPEN and CLOSED data sets taken together indicates that for bedrooms of healthy adults, CO2 concentrations of 1100-1150 ppm may act as a watershed point, beyond which, sleep quality is quite liable to deteriorate.

Window/door opening-mediated bedroom ventilation and its impact on sleep quality of healthy, young adults, by Mishra A.K., Eindhoven University of Technology.

We know that sleep quality affects cognitive and physical development. It would not be a stretch to extrapolate that such development is hindered by high CO2 levels in bedrooms.

VOC Levels

Volatile organic compounds (VOCs) are gases emitted from household items. When a room isn't ventilated, such gases accumulate. They cause upper respiratory tract irritation, headaches and more.

The environmental protection agency of the United States has a good summary on VOCs : Volatile Organic Compounds' Impact on Indoor Air Quality.

Solutions

The basic idea is to exchange indoor and outdoor air.

Warning I haven't tried any of these, and can't gaurantee that they'll work. Please do your own due diligence.

Ventilation Fans with Filters

Such fans exist, but for some reason, aren't common in Singapore. Consider the EcoBreeze 2. It's a ventilation fan that sucks air in, filtering the air as it does so. This particular model has too many bells and whistles for my liking, but the basic idea is good. Here's an extremely old model by General Electric: Ventoglide. Same idea, sucks in filtered air.

Pros

  • Apart from dealing with CO2 and VOCs generated indoors, this approach deals with the issue of outdoor pollutants. Since air is sucked in, air pressure will be slightly higher in the room. This means air will flow out through any gaps, which in turn, means air in the room will be filtered air.

  • This approach is energy efficient. A HDB room setup includes a split air-conditioning unit and a portable air purifier. A single ventilation fan sucking cool filtered air in could replace both those energy drains.

Cons/Uncertainties

  • Off the shelf units with HEPA and activated charcoal filters aren't common in Singapore. This could be a business oppurtunity though. Haze coupled with incense and joss paper burning makes such fans useful to many.

    He told the uncle to use “a little of (his) brain” and common sense and said the burning was responsible for his children’s coughing.

    MAN CONFRONTS UNCLE WHO’S BURNING JOSS PAPER & TRIED SHAMING HIM ONLINE BUT FAILED PRETTY BADLY

  • Noise. This could be a serious issue for babies who can't use ear plugs yet.

  • Effects of increased air pressure in the room. Haven't done much reading on this yet, perhaps the room door must be left slightly ajar.

  • Airflow. I've looked up airflow for ventilation fans. The KDK WALL MOUNT VENTILATING FAN 20CM shifts 580m3 per hour. This means it sucks in the volume of a HDB room every 4 minutes. I do not know whether this is sufficient to cool a room and keep CO2 levels below 1000ppm.

Ducted Air-Conditioning

There are two kinds of home air-conditioning systems, ducted and split. Here's how they work:

  • Split systems circulate refrigerant (typically freon) through the house. Each individual air conditioning unit is simply a fan that blows air in the room over the circulating refrigerant. This means such systems do not draw in fresh air.

  • Ducted systems circulate air through the house. Air is cooled in a central unit, then pumped through ducts to each room. Some such systems allow for fresh air intake and filtering at the central unit. With these systems, instead of large units in each room, you typically see two grills, one expelling air and one sucking air out. Hotels, malls and restaurants use ducted systems. Also, according to a random youtube video, some newer condominiums in Singapore use them too.

Ducted systems with proper air filtering and exchange could be a solution to CO2 and VOC issues. Daikin has a ducted model for residential properties (scroll all the way down for its specifications). Here's a random article on ducted systems by a local aircon-contractor: random article.

Pros

  • Probably can be bought off the shelf.

Cons

  • Expensive. You'd probably need a vented system (in such a system, ducts have mechanical parts that redirect airflow so a single room can be cooled).

Conclusion

I was fortunate enough to spend my early years in a house without much pollution. It was far from roads and my neighbours did not generate much particulate matter. Also, it had good ventilation. Its windows were rickety and porous, allowing for ample air exchange.

Children growing up in tiny, air-tight rooms don't have such luxuries. Efforts should be made to measure air quality in their rooms. Measurements should be compared with empirically derived limits stated in studies/guidelines. Action should be taken to improve conditions.

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