6 Questions To Ask Your Colorado School About COVID And The Air In Your Child’s Classroom

The good news is that this problem can be solved, scientists and engineers say, by filtering and ventilating the air in classrooms, cafeterias and gyms. It is one of the most powerful ways to reduce the spread of COVID, in addition to masks.

But many school districts not focus on that method of preventing COVID-19, despite hundreds of millions of federal dollars allocated for this purpose. Colorado school districts have budgeted $88 million for air quality and spent 1 to 8 percent of the federal dollars they receive on air quality improvements. Applications for school districts to receive the funding are still open.

So, what questions should you ask your district administrators? These questions can be asked by parents, teachers, students and school boards.

1. How is the air in your child’s classroom filtered and ventilated?

Experts say air quality in schools has always been poor, with some classrooms half to a third of the acceptable air exchange rate, the number of times air is changed every hour. So the goal is to increase ventilation and filtration, especially with the Delta variant active.

Scientists and engineers make these recommendations for schools:

  • HVAC systems should be set up to bring in as much outside air as the system will safely allow.
  • Experts have suggested that a minimum of 5 air changes per hour (ACH) is best.
  • Schools with HVAC systems should use MERV 13 filters, the best at filtering out virus-laden particles or the second highest possible – MERV 11.
  • Schools with HVAC systems must open outdoor air valves and turn off demand ventilation controls (which reduce air supply based on occupancy or temperature), said Richard Corsi, an internationally recognized expert on indoor air quality at Portland State University. ,” he said.
  • Open windows (but not two side by side) and control the flow with fans.
Thanks to CDC
An illustration from the CDC shows schools how to keep the air in classrooms safer from COVID-19.

What schools can say and how scientists and engineers respond:

Some Colorado school districts (click here for a link to 25 school district answers to air quality questions) have raised concerns that the MERV 13 filters could put a strain on older HVAC systems. Simply put, air faces more resistance when trying to flow through a MERV 13 filter. While MERV 13s are the best, Jim Rosenthal, a national filtration expert and CEO of Tex-Air Filters, said MERV 11s are perfectly acceptable for school districts and definitely better than MERV 8s or MERV 10s.

Some school districts said upgrades are too expensive, but aerosol scientists claim there are many long term benefits to better air quality at school, such as lower absenteeism, lower asthma and higher test scores. some districts, like the Elizabeth school district, have used federal stimulus dollars to make upgrades and put portable air filter units in every classroom.

However, since school began, it has been too late for many schools to make expensive, high-level system changes to HVAC systems. So …

2. If your school doesn’t have high-quality air filters, has it purchased portable HEPA filtration units for classrooms, music rooms, cafeterias, and gyms?


Portable HEPA (high-efficiency particulate air) filters are a fast, portable, efficient, and relatively inexpensive solution for individual classrooms and rooms.

these units can remove more than 99 percent of dust, pollen, mold, bacteria and the small particles in the air associated with the coronavirus.

In a class of kids who wear mediocre masks and have a good portable HEPA unit, there’s a 92 percent reduction in the inhaled dose of virus-laden particles, air quality expert Corsi said.

What schools can say and how scientists and engineers respond:

Some schools are concerned that portable filters will affect the airflow of the centralized HVAC system. In contrast, most air quality experts have promoted HEPA filters to: supplement ventilation rates.

‘They can only help’ said Mark Hernandez, a civil engineering professor at CU Boulder, who has extensively studied HEPA filters in classrooms. “There is really no downside to room air patterns and recirculation.” However, he said that in order for them to work optimally, they must be installed carefully.

Some schools are concerned that they are too noisy, too difficult to maintain and too expensive. Environmental engineers who spoke to CPR News for this story dismissed many of those concerns. Teachers in a pilot study in Denver said they weren’t too noisy. Replacing a filter takes a few minutes and lasts all year, and the annual cost is about $10 per student, including maintenance and filter replacement.

When weighing costs, experts said it’s important to calculate the cost of inaction.

Thanks to CU Boulder
Students at the University of Colorado Boulder learn how to install air quality monitoring units in classrooms for studying.

How can schools get the portable units?

State legislators devoted $10 million to school grants to purchase portable air filter units for an estimated 15,000 classrooms. Colorado schools have until September 10 to apply for the grants. Districts can also request refunds for units purchased – and can also recover costs through federal stimulus dollars.

3. If schools say they can’t equip classrooms with a portable air filter unit, are the students willing to build one?


Students, teachers and parents can own simple cheap box filter fan which is remarkably efficient at filtering airborne virus particles. Named after its inventors, the Corsi/Rosenthal box requires a box fan, duct tape and four or five MERV 13 filters. It costs less than $100. Another simpler version has one fan and one filter. DIY box fan air purifiers have been studied in classrooms and found to be efficient and effective at filtering out airborne particulates, and are safe, relatively quiet and scalable.

“If you can seal a box, you can make a Corsi/Rosenthal box air purifier,” says Jim Rosenthal of Tex-Air Filters. He said laboratories have tested the DIY units and meet safety limits, such as motor overheating.

What schools can say:

We don’t know how to make them.

How to build one:

The fan pulls air through, the filter (ie MERV-13 or better) removes the virus-laden airborne particles. Be here More resources about how to build such a unit.

“You could have 10-year-olds do a science project and make something that would make their classrooms safer and reduce the number of viruses in the classroom,” Rosenthal said. “It’s a great way to help people learn and feel like they’re helping with COVID.”

The fans for box filters can also: help dramatically with forest fire smoke.

Thanks to Alex Huffman
Alex Huffman built these DIY box fans with MERV 13 filters, which protect against COVID-19, for his daughter’s kindergarten class.

4. Lunch time is one of the riskiest times of the school day for COVID infection. Where and how does your child eat?

When masks go off to eat, exposure increases. Breakfast, lunch and snacks can become breeding grounds for the transmission of COVID-19.


Experts strongly recommend that students have lunch outside. When the weather is too cold to eat outside and officials say children should eat inside, experts advise:

  • Reduce eating time.
  • Don’t talk if you can, play music or a movie instead.
  • At the same time, reduce the number of children in the cafeteria.
  • Increase the distance between the students.
  • Open windows and doors for more ventilation.
  • Ventilate the space between groups of children by spreading out groups for 15 to 30 minutes. An infected person doesn’t have to be right in front of you to infect you. Aerosol cans can stay in the room for hours.
  • Place extra portable HEPA filters in the dining area.
210318-HODGKINS-ROOM-132-JBJenny Brundin / CPR News
The students in room 132 have lunch together on 10 March. “Now that we’re not looking at a screen all day and we actually see each other and sit together over lunch, I think we have more of a friendship than when we were on Zoom,” said one of them, Amaya.

What schools can say and how scientists respond:

The Colorado Department of Education guidance for schools is not talking about lunchtime. And some neighborhoods prohibit students from eating outside because it’s a logistical challenge.

“Having lunch indoors at school is like having a pool full of kids holding their bladders all morning and then putting them all in a hot tub and letting them defecate in one sitting,” says DU’s Huffman.

Thanks to Marwa Zaatari
An illustration engineers use to explain how the coronavirus can spread among children over lunch if they can remove their masks.

5. Does your school need face masks?


Experts say that the Delta variant requires a good mask. Multiple studies show that masks have been proven to reduce risk in classrooms. Masks work through filtration, not seven.

“They work, there’s no getting around them,” said Linsey Marr, a Virginia Tech civil and environmental engineer who studies the spread of viruses through the air.

When buying a child’s mask, the priorities are comfort, fit (leakage on the sides is like having a hole in your mask), and filtration. N95s are not a good fit for children. The KN95 (Chinese) and KF94 (Korean) do have children’s sizes, but you have to watch out for fakes. There are also cloth masks with a built-in layer of filter material, which filter out more than 99 percent of particles when they fit properly.

Where to get good children’s masks:

Here are some recommendations about masks for children, curated by Marr and Aaron Prussin of Virginia Tech, and others Child Mask Recommendations of the Clean Air Crew.

6. How many exhalations of other children does your child inhale?


  • Carbon dioxide monitors are a guide to how well ventilated a room is or how much of other people’s exhalations children are breathing in. Full classrooms mean CO2 levels are likely to be higher, with students breathing more of each other’s air. That means that if there is someone with COVID, the concentration of COVID particles in the confined space increases.

CO2 monitors, with measurements throughout the day, can help determine where more airflow is needed, or changes in HVAC systems. All British schools will be monitored.

Some experts say it’s not a one-size-fits-all, as classroom architecture is different and they need to be installed thoughtfully. But others, such as Elizabeth School District Superintendent Douglas Bissonette, said even a portable CO2 monitor can just be a guide, a handy indicator of how much fresh air is coming in.

“We’ve found it stuck in a few of our rooms and that’s because our HVAC wasn’t working properly and then served as an indicator for, ‘We need to fix it…or we’re going to open windows.’ ”

To see how your district responded to questions about what it did regarding classroom air quality, click here.

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