Indoor Air QualityIndoor Air Quality Terms

CO2, VOCs, PPM, Radon, PM2.5……

You’ll have heard of CO2, but how many of the other indoor air quality terms have you heard of, let alone know what they are and how they can affect your health?

Many of these affect us on a daily basis without us knowing.

Ever feel sleepy in a meeting room? Ever find you get more headaches when at your office desk? Just can’t concentrate in an open workspace?

Yes, boring presentations, screen time and distractions have an impact, but more often than not, poor indoor air quality levels (even in some of the best Grade A buildings) are affecting us.

So let’s take a look at some of those acronyms and terms that we find on indoor air quality sensors and see how they might affect us.


PPM – let’s start with PPM as you’ll see it come up a lot below.

Parts Per Million.

This is how much of a pollutant can be found in the air. Specifically, concentration found per million. This is similar to how a percentage is measured out of 100.
The higher the number, the higher concentration of the pollutant in the air.

CO2 – One we will all have come across. One that we expel with every breath we take. But do you know how it affects us?

Carbon dioxide.

Common in busy areas, and even more so in closed rooms such as meeting rooms, CO2 has a fast and substantial impact on how we feel in the office. High levels of CO2 can lead us to feel lethargic, drowsy, fatigued, and restless and can drastically reduce cognitive performance and decision making. Even low to medium levels of CO2 can start making an effect on how we feel, negatively affecting cognitive function and energy.
CO2 Indoor Air Quality Thresholds:

Low – 400 – 1,000ppm
Medium – 1,000 – 2,000ppm
High – 2,000ppm +


Radon is a radioactive gas that has no smell, colour or taste. That makes it tough for us to detect. It also affects us over the long term, making it even harder to attribute.

Produced from the natural radioactive decay of uranium, which is found in all rocks and soils, Radon escapes into the air where it decays. As we breathe it is deposited on the lining of our airways. Outdoors Radon concentrations are low but indoors, poor ventilation can lead to dangerously high levels.

Consistent exposure to high levels of Radon is a major cause of lung cancer.

Despite starting in the ground, Radon leaks into buildings everywhere. Rates fluctuate all the time and different buildings are affected differently. Due to these fluctuations, it is better to take mean measurements quarterly, or at least annually.

Average indoor Radon levels: 1.3 pCi/L
Target less than 2 pCi/L


VOCs – Airborne chemicals emitted from everyday household products with some short-lasting and some long, negative effects.

Volatile Organic Compounds.

Common short term effects include eye, throat and nose irritation, skin irritation and headaches. Most offices do a good job of keeping VOCs low thanks to the fact most suppliers provide lists of all chemicals used in their cleaning products, paints, adhesives, materials or other such products.
Some of the chemicals include Benzene, Formaldehyde, Ethylene glycol, Methylene chloride, Tetrachloroethylene, Toluene.

Considering there are a number of different chemicals within this category, thresholds differ. Most IAQ (indoor air quality) sensors measure ambient concentrations of a broad range of gases associated with bad air quality.

PM 2.5 refers to particulate pollutants that are 2.5 microns or smaller in size.

Particulate Matter 2.5 is particularly dangerous as they are small enough to bypass our bodies’ natural defences like noise hair and mucus. That means the potential for more respiratory diseases.

Filters and controlled lower fan rates, hence more pro-active ventilation systems which reduce the occurrence of fans suddenly blowing at full power, can help reduce the spread of PM 2.5.

PM 10 – As you can probably guess, PM 10 refers to particulate pollutants that are 10 microns or smaller in size.

Again, being inhalable by the lung, they are particularly dangerous. Often in buildings, PM 10s can be a result of construction dust or similar when maintenance works are done. Also included is mould which has very fast-acting effects such as headaches or itchiness of the throat and eyes, as well as longer-term issues. Understanding when these levels are high can help you identify a cause and similarly to PM 2.5, understand if fan speeds should be lowered to prevent spread in the air when PM 10 is high.

Technically, there isn’t a safe level of PM2.5 or PM10, as any amount of particulate matter in your air isn’t a good thing but it often exists at low levels and sometimes can increase periodically due to a new activity or change in the environment. So one to keep an eye out on levels over time to see any spikes.

Humidity – I’m sure you are aware of what humidity is but maybe less so on how humidity levels affect our health in indoor environments.

High humidity of indoor air (over 40–50%RH) can lead to condensation and a higher risk of microbial growth on surfaces. This is often caused by inadequate ventilation and can be a big problem in typically high humidity countries such as the middle east.
Not only can high humidity cause damage to walls, furniture or windows; but it can also lead to mould and as mentioned before, that is bad for our health.

All in all, offices can be healthy, productive and sustainable environments, and that is what today’s tenants are demanding.

Running a company that helps commercial real estate owners maintain optimal indoor air quality whilst accelerating their journey to net zero targets, I realise I had taken for granted knowing many of the terms and their effects on us as humans. The more we know about the effects of the air we breathe, the more we can do to ensure we have the best environments to live, work and play in.


Learn more about how CubeOS can support you in maintaining optimal indoor air quality wherever and whenever people are in your buildings (and how you can reduce energy waste at the same time!)