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The best indoor environment for studying is free from distraction. A recent review article that examined 21 studies on how both students and teachers get distracted, found that “neutral” levels of noise, temperature, lighting, and carbon dioxide were best for learning.

What makes for neutral is different for everyone, but most of what the research found is not surprising. Neutral sound levels are quiet enough to hear what’s going on and without noticeable variance. Neutral temperatures are generally between 18 - 30°C or 64.4 - 86°F, depending on the weather outside. Neutral lighting that helps with focus is slightly blue, or around 4000K. Neutral carbon dioxide, or CO2, is a little different because of what high CO2 levels can mean.

The presence of carbon dioxide, or CO2, doesn’t just mean that people are exhaling, it also means a lack of ventilation and fresh air coming in. Research has shown other pollutants that build up along with CO2 might have bigger negative impacts on learning than CO2 alone and that persistent unpleasant odors have several negative effects. Let’s take a look at the research to learn more about how to create the best air for studying and what to prioritize for each unique situation.

Modern windows cracked open to let in cool air

Start with carbon dioxide

One of the reasons scientists have been finding that CO2 levels impact academic achievement is that CO2 sensors are inexpensive (about $50) and easy to find. A lot of research has shown that carbon dioxide builds up quickly in crowded rooms and has a direct impact on decision making ability.

In rooms that are small like dorm rooms or crowded like classrooms, CO2 is likely to build up fairly quickly. After just an hour the composition of the air behind closed doors is very likely to have changed for the worse. In a classroom setting with 20 or more students, CO2 can be high enough to impact cognition within about 30 minutes.

How much CO2 is too much

There are a few ways to tell if the CO2 concentration in a room is too high. The best is if spending time in the room gives you a headache, makes you feel tired, or spurs other neurological effects.

CO2 monitor showing a reading of 574 ppmCO2

Another option is using a CO2 meter to directly tell you what the concentration is. You want to keep it below 600 ppm. As levels rise, the following complications can occur.

Remove CO2 with ventilation

The CO2 that builds up as a result of people breathing can be dispersed with outside air ventilation. Basic building guidelines set in place by ASHRAE recommend at least 0.35 air changes per hour, or about one third of the room’s air exchanged with outside air per hour. This may not be physically possible or economically feasible in all spaces, and with more people more ventilation is required.

Open windows or doors to the outside or hallway if possible, or ask for them to be opened. Opening the window for about seven minutes can replace half the air in a room and drop CO2 levels halfway toward lower outdoor concentrations. Use HVAC ventilation if available.

Move on to smells

Stinky dorm rooms or strongly scented beauty products can affect your grades. Persistent undesirable smells reduce our overall feeling of well-being and can foster a combination of bad moods, including depression, fatigue, confusion, anger, and tension. They can also be major distractions and make it difficult to focus on complex tasks. One study found that proofreading was negatively affected by a bad smell while simple math was not.

Messy student's bedroom with dirty clothes and leftover food

Most indoor odors come from food and living bodies. All smells are what are known as VOCs, which are chemicals that float through the air and are emitted from a wide variety of sources. While most VOCs are harmless scents, high levels can react in the air to create unhealthy particles. Releasing large amounts of VOCs when using strong-scented cleaning products, for example, can expose your home to unhealthy levels of particle pollution.

How much smell is too much smell

There are a few indoor smells to watch out for, like mold or smoke, that should be dealt with immediately, and the source of any consistent or potent smells should be identified. When smells do build up it’s important to open the window or otherwise increase ventilation, because that usually means that CO2 has built up as well. Opening the window, turning on the fan, or finding any other way of ventilation is particularly important if cooking.

To be absolutely sure, there are devices called TVOC meters that can measure the total VOCs in the air. If the TVOC is over 500 ppb for extended periods then air quality might start to get worse.

Remove smells with source control

Finding the source of offensive smells is the first step, so remove or clean any gym clothes, fragrances, or old food. Keep laundry in a container and food waste in the kitchen to minimize any stray items that may linger and start to smell.

Smells can soak into walls, floors, and other surfaces then slowly release over time in a process called adsorption. To neutralize odors that have soaked into surfaces, don’t make air quality worse by spraying anything or using a strong-scented product to cover them up. Instead, use warm water and soap to remove the food or other debris.

If smells persist, sprinkle baking soda on the stinky surface, leave overnight, and vacuum it up in the morning. A box of baking soda can also be placed anywhere in a room to absorb odor from the air. Keep in mind that it will eventually become saturated with smells and will need to be replaced every few weeks.

Activated carbon air filters can also help, but the VOC levels in the average household can saturate one kilogram or two and a half pounds of activated carbon per month. If possible get a carbon filter with at least that amount of carbon per month it is used. Molekule’s PECO-Filter was designed to destroy VOCs continuously regardless of carbon saturation.

Rendering of viruses and airborne pollutants

Control biological aerosols

Biological aerosols, or bioaerosols, are particles in the air that are biologically active. This includes viruses, bacteria, mold spores, pollen, and other bits that can trigger allergies or make us sick. Infections can make us miss school or work, but it’s also true that allergy triggers in the air can be distracting. One study found that when pollen counts spiked, High School students, even those without allergies, performed significantly worse on tests. Another study found that during ragweed season (late summer and fall), the cognition of people with allergies slowed down to some degree.

Most airborne infectious pathogens come from the presence of other people. But bacteria like staph and strep can live on dust particles that float through the air, and mold spores are literally everywhere.

When there is a biological problem

The sources of bioaerosols span every known form of life, so knowing when there is a problem requires slightly different attention for each one.

  • Viruses are the most fragile of bioaerosols but also the most deadly. They remain viable in the air for hours, so during outbreaks or flu season crowded rooms are very likely to be dense with viruses. High CO2 also comes with a high concentration of viruses.
  • Bacteria cause fewer airborne infections than viruses, but diseases like whooping cough, strep throat, and tuberculosis are all caused by bacteria that can travel through the air. Bacteria can form hearty spores that persist for months or years.
  • Mold grows in colonies that must have a source of water. Small amounts of mold spores cover virtually every surface, so if there is a smell of mold or any consistently wet materials, mold is likely to be growing.
  • Pollen is released by trees, flowers, and weeds all year round except winter. Most people have the worst allergies in the springtime when trees and flowers are reproducing.
  • Allergy triggers can also be pet dander, pet hair, insect leavings, or many other biological particles.
Hand wiping away dust from a wooden surface with sponge

Clean the air and handle the dust

These types of particles exist in all environments, but here are a few ways to keep their effect minimal.

  • As we discussed above, the best way to handle the build up of any of these bioaerosol particles is with ventilation from open windows or doors. If those solutions are not available, an air purifier can remove particles, just be sure to get one that can reduce the tiny viruses as well.
  • Dust can harbor a wide array of pathogens and allergy triggersWeekly vacuuming and wiping down of surfaces can cut down on mold spores, bacteria, pollen, and other detritus.
  • For mold specifically, be sure to handle any leaks or other persistent sources of moisture so there is no mold in your space. Breathing mold spores all the time can cause serious problems including not just allergies but also mental and emotional issues. If there isn’t an obvious solution, contact a mold specialist, your landlord, maintenance department, or whoever can help.
  • For people allergic to pollen, weekly vacuuming might not be enough. Try to remove clothing and shoes when coming in from outside to avoid tracking in pollen. Avoiding any pollen in the bedroom is most important because of how much time is spent there.
  • Air purification can also be a way to reduce pollen and other allergy triggering particles in the study area or bedroom. Whole pollen grains and mold spores often fragment into smaller pieces that can be easily inhaled and deposited in the lungs, so be sure to get a purifier that can capture extremely small particles and destroy organic material, like a Molekule purifier with PECO.


Whether preparing your dorm room or bedroom for studying, don’t neglect air quality. There is no substitute for ventilation, but the right air purifier can minimize pollen, mold spores, and smells for a less distracted learning experience.

Keep an eye on this blog for more science-based tips, and our FacebookInstagram, and Twitter accounts for everything on the science of clean air.


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