Facts & fables about indoor air quality

Is CO2 harmful? What is the ideal working temperature? Discover the answer to these and more questions with Clairify.

Over the years, we have encountered various assumptions about indoor air quality. We love to share our knowledge with you, and that's why we've collected our favorite assumptions and put them to the test: is it fact or false?

Sensors that measure TVOCs also measure smell. 

This can be true if talking about single VOCs, but the same claim does not necessarily apply to TVOC values. This might sound weird, so let us explain.  

While there are several odorless VOCs, there are also a lot of VOCs that are indeed odorous (smelly). Therefore, following the logic of smell = VOC, there is a popular assumption that if there is something smelly in the room, the sensor should be able to detect it.   

However, a VOC sensor is not made to mimic the sensitivity of the nose. Our nose is explicitly designed to detect certain VOC odors, even at very low concentrations. In fact, our nose can detect smells in the nanogram range.  

The TVOCs value, on the other hand, is the sum of the concentration of different measured chemicals. So, it might happen that your nose detects an odor coming from a very specific VOC, but the sensor measuring TVOCs won't detect it because of the low concentration thereof. Odors are a good indicator of the presence of a VOC in the room, but not of the concentration of the VOC. 

Therefore, we mark this statement as a FABLE.

CO2 is bad for your health. 

We often hear that we need to ventilate a room because a high concentration of CO2 might make you dizzy or give you a headache. But, is this true? Is CO2 bad for your health?

Well, this one is a tricky one. CO2 on itself is not bad for your health. In fact, we need CO2 as part of our daily life and breathing functions. In extraordinary situations in long continuous exposure, high concentrations of 5.000 ppm CO2 can be harmful to your health and well-being, since it could affect the level of oxygen our bodies are getting. This lack of oxygen could result in headaches, dizziness, and drowsiness, but also affect your cognitive performance and your concentration. However, these concentrations are very unlikely to occur indoors. 

We learned something very interesting at the HealthBuild Conference about this. It is likely that CO2 is not the cause for all these symptoms, but rather the VOCs in a room. What tends to happen is that CO2 is easier to measure and report on than VOCs and, therefore, it serves as a guideline for the air quality in a room. When CO2 starts rising, VOCs usually rise, too; affecting your health.  

So, if we want to be very specific:

Is CO2 bad for your health? We mark this statement as a FABLE.
Is a very high concentration of CO2 harmful? We mark this statement as a FACT.

Do you want to know an interesting fact about this? When submarines became part of the naval force, people needed to know what safe levels of CO2 were. In 1961 they concluded that values up to 40.000 did not affect neurobehavioral performance. That is way over the limits we set today.  

You can lower relative humidity by turning on the heat. 

To understand this point, we first need to understand what is relative humidity.

In summary and in a very simplified explanation, relative humidity is the amount of water air contains relative to what it can maximally take up. However, this number varies depending on the air temperature. For example, hotter air can take up more water than colder air.  

So, what happens if we turn on the heat? Because hotter air can take up more water, relatively seen we would have less water compared to what the air can maximally take up. Thus, reducing relative humidity. It sounds confusing, so, let's put this into (very basic) numbers to make it a bit more graphic:  

Relative humidity is expressed in percentage and can be expressed either in terms of pressure or density. This means that it is measured like this:

(Current water density in the air ÷ Maximum capacity of water density) × 100.  

Let's say that the air in a closed room with an average temperature can take a maximum water density of 100. If the current water density is 60, then the relative humidity would be (60/100) × 100 = 60%.  

If we increase the temperature, allowing the air to have a larger maximum capacity of water density, for example, 120, the relative humidity in that same room will look like this (60/120) × 100 = 50%.  

Therefore, this statement is marked as a FACT.  

The ideal temperature to work is 21 degrees. 

This has been considered accurate for a very long time and it has been argued that it is the ideal temperature for office spaces and working environments.  

However, this assumption has recently been busted. Research has proven that people are much more adaptive than we initially thought. Suppose we expose people to high temperatures for a long period of time. In that case, they can get used to the temperature rather easily, and no impact on their productivity, comfort, or well-being can be measured

A change in any of the previously mentioned factors occurs mainly when people are not used to the temperature yet and they experience a sudden change in room temperature. But in the end, the thermal comfort of people tends to be much more ligated to the humidity and ventilation level in a room than only the number on the thermostat. Take a look at this example in our article: Thermal comfort: Is your building truly healthy?

For this reason, we mark this statement as a FABLE 

A new particulate matter filter works better than an old one. 

Believe it or not, a clogged filter filters out more than a fresh one. However, old filters might present another problem. When filters are not replaced in time, microbes and fungi can grow in the filter with more ease, causing potential health issues.   

Therefore, we do recommend replacing filters in time. A nice additional benefit of changing them in time is that it saves energy in the building, as pushing air through a clogged filter will require more energy than pushing it through a clean one.  

So, even though the particulate matter filter itself does not work better just because it’s new, the overall system does.  

For this reason, we mark this statement as FACT.   

Learn more about how monitoring all these parameters might affect your health in our latest article: Healthy buildings & Health.

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