Ventilation Measures

Short Description

All classrooms that are occupied with students have been reviewed and have a Ventilation Certification sign on the door. There are two types of certification, Mechanical and Portable filtration. The signs are similar with different check boxes indicated. Mechanical certification (built-in classroom system) is identified via the three left hand boxes containing required information: an occupancy amount, Merv-13 filters, and a 30CFM. Portable filtration is indicated with the separate HEPA filter box checked. See below. Our focus has been on classrooms of a population of 10-15. Right at school, support spaces, overflow rooms, or specialist rooms are not included. Support spaces will be added to the certification after the main classrooms have been addressed District-wide. Additionally, all Mechanically Certified spaces will get a smaller, portable HEPA filter as supplemental filtration in the classrooms.

Mechanical Certification Sign

Portable Certification Sign

Long Description

Here are the steps we've done and criteria we established to ensure the healthiest environment possible:

There are essentially two components of the HVAC system: Fresh air (ventilation) and recirculated, filtered air (filtration). The current guidelines are to increase outside air to dilute the interior air (ventilation) and install new, clean filters (filtration). The guidelines prefer using MERV-13 air filters if the units can handle them but recognize many older units may only be able to use a MERV-8. The guidelines do not require the filter upgrade because many older hvac units cannot function effectively with a MERV-13 filter because they create too much of a pressure drop. That was the target we met previously strove for. You can think of it like breathing through your cloth mask is like the units equipped with a MERV-8 filter that the units were designed for but breathing through 10 masks stacked up would be the MERV-13. That is just an example of the pressure drop and airflow to help understand.

We continued to work to improve the air ventilation and filtration and have set up new classroom guidelines that we are using to certify the classrooms.
1. The first guideline is filtration. We have done extensive research and have found high performing, low pressure drop MERV-13 filters that will work in our older units. Back to the mask example, that is like wearing an N95 mask instead of a cloth mask. We have replaced all filters in the District with MERV-13. This includes custom ordering and modifying some older units to work with the MERV-13 filters. Our new guideline is that every room must have MERV-13 equivalent filtration as a baseline.
2. Our second guideline is ventilation. We established a baseline of measuring double the code required fresh air per occupant of 15 CFM (cubic feet per minute) of air per occupant. There are a number of ways the code allows that number to decrease in order to save energy but we are disabling those features to provide a baseline of continuous 30 CFM per occupant. In many cases we will have more than that depending on the age and design of the system but we are setting that as a baseline. Additionally, opening windows will increase that.
3. We then test the rooms. This is a simple pass/fail test. If it meets those two criteria, MERV-13 and 30 CFM, in gets certified. If it does not meet those criteria then we put a portable filter in the room. All portable filter rooms will also be certified under the portable filter option of our certification.
4. We also are putting portable filters in rooms that we do not have time to test. We will continue to work through the District and test the units. When we test a room, if it passes, we will pull the portable unit out of the room and re-certify it as passing with mechanical ventilation. If a room fails, that does not mean the system does not work. Sometimes it can be a 5-minute fix. Other times it could be a 5-hour fix. And yet other times it could require a part that has to be ordered. We are not letting a failure get us bogged down at the expense of serving the District as a whole. We will install a portable filter and then come back to troubleshoot after we have provided for the safety of the rooms. Rooms that have not passed as of 12/15/2020 will continue to be serviced to hopefully have them pass mechanically in the future.
5. As of 12/15/2020, testing will be complete on every campus and we will begin shifting the portable filters out of the primary spaces that pass the certification testing and into the middle school spaces or to be repurposed in auxiliary spaces such as rainy-day lunches. Once a room passes via mechanical ventilation, we are going to remove the portable filter and change the certification checklist. Based on feedback from the staff and community, once a room meets the mechanical certification requirements, we will add a small HEPA Filter in exchange for the larger filter to provide a little more filtration in those rooms.

We are additionally doing air quality testing to further enhance the systems as a third round of continued efforts to improve the effectiveness of the classrooms ventilation and filtration. This is the needlepoint bipolar ionization that we have presented briefly in past board meetings. Based on our test results, we are confident on going forward with the new technology and have been doing test installs to determine their effectiveness and compatibility with our District technology. The purchase of the needlepoint bipolar ionization units will go before the Board on December 15, 2020 for their review and direction.

The best way we've heard this explained is to imagine a swimming pool. The ventilation is a garden hose filling the pool. The filtration is the pool cleaning system. COVID is a child peeing in the pool. You would like to filter that water to clean it up but your filter can only do so much so you also need to keep adding fresh water. The more fresh water you have, the more diluted that pee is. So we are trying to both add water and upgrade our filtration.

Frequently Asked Questions

(Otherwise known as everything you never thought you’d care to learn about filtration)

This is meant as a resource and a guide to the myriad of questions around the topic.

General Questions

Where do I find information on the small Winix air filter or large portable filters:

For the Winix filters, scroll down to the Winix section below.
For large portable filters, scroll down to the portable filter section below.

You've mentioned Needlepoint Bipolar Ionization. What is it:

We are taking this technology to the Board on 12/15/20 and will provide more information shortly.

What are the exact guidelines of the Santa Clara County Health Department:

The guidelines are what we initially targeted and what most Districts are doing that are back to school. That was our direction back in the summer and early fall. In late September, as a result of the information we learned from the first Hays commissioning, as well as ongoing input from consultants, engineers as well as the faculty, staff, and parent community. The Santa Clara County Health guidelines are to open the windows to increase outside air. Absent that, they recommend MERV-13 filters when windows cannot be opened. To be clear, we met those guidelines in a majority of our classrooms prior to the certification standards we established and the upgrades we commenced.
The Direct language is: Increase ventilation by increasing outdoor air circulation (e.g., by opening any operable windows and/or doors) or using high-efficiency air filters and increasing ventilation rates.
Footnote: Increase circulation of outdoor air as much as possible by opening any operable windows and doors, unless doing so would pose a health or safety risk to individuals using the facility (e.g., allowing in pollen or smoke or exacerbating asthma symptoms). If opening windows poses a safety or health risk, maximize central air filtration for HVAC systems (ideally with a targeted filter rating of at least MERV 13).
That is an important distinction. The County's guidelines are to open doors and windows for increased ventilation by outdoor air or have increased central air filtration with "ideally" MERV-13 filters. There is a lot of confusion around the terms. I've had conversations with engineers that use the terms loosely. What the county guidelines are calling for is ventilation or filtration. It is a little confusing the terms seems like the same but they are not. We try to explain it on the ventilation website so I encourage you to look at that explanation but basically the County is calling for either increased outside air or improved and increased recirculated, filtered air.
The District chose to meet and exceed the County's guidelines by doing both. We mechanically set an increased outside air component (that is the 30 cfm/ occupant) and then we improved filtration with the addition of MERV-13 filters.

Our buildings are old. How can we trust the systems that are built in the 1950's:

Almost all of the 1950's systems have been removed at this point. There are only a few select locations with original systems.
A majority of the District mechanical units were installed in 2001/2002 or later.
The original design of many buildings was for radiant heating and window ventilation. The radiant would often leak and was therefore abandoned throughout in the late 90's and early 00's.
The performance of your mechanical units has not changed much in that time and has only started changing in the last 8 years or so. Even with that, many new rooms are designed for MERV-13 but specified with MERV-8 filters for energy savings measures. Our District standard was MERV-8 prior to COVID-19. This is typical in many office buildings, schools, and other public spaces.

Do I leave my doors and windows open or closed:

Initially we've said either is fine. Upon further review and consultation, our recommendation is to close the doors and windows with either certification method.
Mechanical Certification: The certification process is to ensure a measurable amount of outside air that is brought into the room to dilute the air. We are effectively controlling the effect of open doors and windows. Due to that set amount, we are recommending doors and windows closed so the mechanical ventilation can do the work it is certified to do. The built-in systems are providing a lot of outside air. In many cases far more than the minimum baseline we've set. You should be fine with the doors and windows closed if you have mechanical ventilation.
The portable filters don't have mechanical ventilation but they trap most of the COVID particles in the HEPA filter. With the doors/ windows open, you will dilute the air more but also make the filter less effective and take longer to trap any COVID particles if you have a sick person in the room. Therefore, we are recommending keeping doors and windows closed with the portable filters as well.
Now that the weather is getting colder, it will be more comfortable in the rooms with the doors and windows closed.
Per standard security protocols, you should close your windows at night.

Can I just bring in or use my classroom fan:

No. Do Not Use Fans.
Fans create turbulence which will kick up any COVID-19 particles that fall to a surface.
The way the filters pull the air does not create the same kind of turbulence.

My building / room does not have windows. What about my room:

Based on our certification process and our recommendation to leave doors and windows closed (see doors and windows above) the rooms are certified even with no windows.

My building / room is a sustainable building designed with passive ventilation and not mechanical systems. How will you certify that room:

Based on our certification process rooms with passive ventilation or radiant heating and no ventilation are certified based on the portable air filters.

Why was my room not safe and needed a portable unit and now is considered safe and the portable filter is removed:

Your room was never considered "not safe". It was considered not tested.
As you can see from the process outlined above in the long description section, we put portable filters in the rooms prior to testing them. That was our means of certifying as if there was no mechanical system.
Some people have missed this in the volumes of information about the reopening measures. Trust us, we've repeatedly said this is our process. The decision to purchase the portable filters was for two main reasons:

We knew we had some rooms that would not meet our certification and
A factor of time and the desire to certify before children return to the rooms since the independent consultants had a limited availability and would not be able to test all the sites before we returned to school.

When can we see the data for our rooms:

We are working with the consultants to get the results in a publishable format.
We still don't have the data on many of our sites which is why our portable filters are still deployed.
WE DO NOT CERTIFY A ROOM UNLESS THE REQUIRED OUTSIDE AIR MEETS OUR CRITERIA. IF WE DON'T HAVE THE DATA, WE CERTIFY WITH THE PORTABLE FILTERS.
We hope to publish reports soon showing the measurements for every room.

What are the air change ratings (ACH):

Many recommendations looks at air changes per hour (ACH) but that metric only looks at filtered air and we have chosen to certify based on dilution with outside air or filtered air with the portable filters. So the ACH numbers would represent different things.
The outside air turnover is about 3-4 times per hour depending on the room but that rate is more important depending on the number of people in the space. (ie if you have 2 people in the space, filtering the air is more appropriate since the air exhaled is highly diluted in the large space but if you had 100 people in the space you would really want to turn over that air with a lot of outside air to dilute it.)
Many have heard of 6 air changes which is actually part of the ASHRAE recommendations for dealing with COVID-19 but we don't feel that is sufficient enough. That is why we are not using that as a certification metric and are instead focusing on the dilution of the air with the amount of outside air per occupant as our determining factor.
Our consultants recommended and many schools are following the 6 ACH guideline for filtered air. We chose to exceed those requirements and instead are exceeding that by setting the outside air metric.
You can have MERV-13 filtered air ACH, HEPA filtered air ACH, outside air ACH and all of that changes based on the room volume. Since that metric is more variable, we chose to focus primarily on the amount of outside air for the occupancy to emphasize the dilution.

Which is better, Mechanical Filtration or Portable filtration:

Based on these factors, in our opinion, they are about equal in efficiency.

Which solution is safer,Mechanical Filtration or Portable filtration:

For a comparison of the mechanical ventilation to the portable filters they are partially doing different things and it is a little like comparing apples to oranges. The portable HEPA filters do not provide outside air. The mechanical classroom systems do.
The mechanical ventilation is both diluting and filtering the air
The portable units are only filtering the air but are doing so at an even higher rate that is closer to Hospital operating room grade. Some studies suggest the HEPA level will catch almost all of the COVID-19 particles while other studies suggest not.
So there is no clear winner between the two directions. They each have their own tradeoffs. As you can tell by the noise of the portable units, the increased filtration requires significantly higher airflow while the built-in system allows us to mix in fresh air to dilute the air more without the added noise.
If we go back to the previous point about air changes, the HEPA filters are providing anywhere from 2-4 ACH depending on the space. The mechanical method is providing 6-10 ACH depending on the space. The tradeoff is the HEPA filters block more COVID-19 particles but at a slower rate. If we were to install HEPA filters equal to 6 ACH your rooms would be a wind tunnel and you would not be able to teach.
We are trying to balance all aspects of the environment and the portable filters at the lowest possible setting that we are comfortable with is still too high for many teachers. Most teachers thus far have been happy to have the portable filters removed from their classrooms as they are noisy due to the added air required to push air through the HEPA filter. So again, this is a balancing act.
Additionally, we did a series of baseline air quality tests in comparable sample classrooms with both MERV-13 filters and compared them to the HEPA filters. We tested for mold, allergens, VOCs, etc and the results were similar supporting the effectiveness being similar.

Can we bring in our own air filter:

You are welcome to bring in your own but the District will not maintain them. We are planning on providing sufficient ventilation/ purification with the district equipment.

I thought the systems were off except when we turned on the heat for a limited period of time:

That is how our systems used to be set up to conserve energy.
Part of the commissioning process we spoke of was to change those settings so they provide outside air all day long. We start at 5:30am and turn it off at 7pm.
The heat works independent of this setting

What are other Districts doing:

Every District is currently asking the same questions we have been.
Many are choosing to meet the first step criteria outlined above and stopping there.
A few Districts have upgraded to the MERV-13 filters including East Side USD, Las Lomitas ESD, and others.
Many Districts bought smaller HEPA filters similar to our additional filters that we are adding.
We were the first to commit to the portable commercial grade filters as a backup and were therefore first in line. Two other Bay Area Districts have also just ordered these units.
We've talked about the bipolar ionization (step 3 outlined above) that we commissioned air quality tests before deciding. Other Districts bought them outright and are now testing them. Those Districts include Acalanes, Berkeley, and Bakersfield. Others are considering adding bipolar ionization. Many are waiting for our test results from the vendor.
Some Districts are considering installing complicated fan systems with UV light. We researched those and they are less effective and considerably more expensive than the other options we are pursuing.

Winix Filters

What is the use of the Winix filter:

The District has added the smaller Winix HEPA filters to all rooms that are mechanically certified
The rooms that are mechanically certified all now have the addition of a smaller Winix filter.
The filter is a little extra filtration on top of the mechanical filtration.

How does the Winix filter:

The District has added the smaller Winix HEPA filters to all rooms that are mechanically certified to give an extra layer of HEPA filtration
The filter adds another air change to the classroom air that is cycled through the HEPA filtration
The Winix helps balance an additional layer of HEPA filtration with a lower noise impact from the larger filters.

Where else will the Winix filters be used:

We will certify the smaller rooms that are being used by specialists for one to one support and small group activities because the larger portable filters overpower those rooms.

What settings should the filters be set to:

For classroom support, It is up to you to set it as you wish depending on the fan speed that you want.
There are 4 levels of airflow. The highest setting is the setting to give the maximum amount of filtration for added support. The max setting will do 1-1.5 air changes in a standard classroom. We do not know the fan speed of the other settings.
The timer should also be set to no more than 8hrs

Why are we not leaving these on full time like the larger filters:

The filters have three filters in them. The prefilters will be changed when we change the other filters on site but they are small filters
The HEPA filters are smaller than the large portable filters which are rated as a 10 year filter. The small HEPA filters are rated for a year of normal use so we do not want to leave the filters on 24hrs a day.
The HEPA filter will not be changed before the one-year point.

MERV Filters (Mechanical Certification)

What filters do I have:

Almost every occupied room with mechanical ventilation now has a MERV-13 filter. If they are not upgraded yet, they will be in the next week. Then we will shift to the next wave of openings to make sure those rooms are upgraded.
The portable filters have a MERV-8 prefilter and a HEPA filter

What is all this MERV-business:

MERV-is the Minimum Efficiency Reporting Value and is a measure of the effectiveness of an air filter. That translates to how small the particulates are that will pass through the filter.
MERV- 8 blocks particulates at 3 microns
MERV-13 blocks particulates at .3 microns
HEPA filter is considered MERV-17 or higher and blocks smaller than .3 microns

Where are the different filters used:

MERV-8 are used in schools, commercial buildings, high end homes, and industrial settings
MERV-13 - 16 are used in Hospitals for inpatient care and surgery and high end commercial buildings
MERV-17 - 20 (HEPA) are used in cleanrooms, radioactive situations, and pharmaceutical manufacturing

How effective are the filters:

MERV-8 filters block out particles down to 3 microns
MERV-13 filters block particles down to .3 microns
MERV-17 - 20 (HEPA) block out particles down to .1 microns

How effective are the filters at blocking COVID-19:

MERV-8 reports vary but they potentially block about 20%
MERV-13 reports vary but most reports indicate 75%-80% filtration
MERV-17 - 20 (HEPA) potentially block 99.0%- 99.9% of COVID (studies vary)

How often are filters changed:

Filters traditionally were changed every 6-8 months. Now we have increased that to every 3-4 months.
You do not need to put in a work order to change them, we are doing it continuously and tracking the changeout.

How do we know if you've changed the filter or not:

For now you have to trust us that every unit has been changed to MERV-13 prior to the independent testing. When we publish the test results, you will see they are all MERV-13 filters
We are gathering the data for the next filter change out and will post it here.
As far as we know, we are the only district to develop a certification process based on room dilution with double the code required amount out outside air.

Large Portable Filters

What is the role of the main office purifier:

We added a portable purifier at every main office location. This is because there are various interactions from public, sick students, or faculty pass thru.

What about Offices and support spaces:

The theory is smaller specialist rooms or offices do not have a large number of students or can adjust their practice to provide services outside, in larger rooms on campus, or even remotely. This determination is from various conversations with the sites about how these rooms are functioning. If special considerations are needed, please contact me and we can discuss the unique situation.
As more students have returned, more of these services have been performed in their traditional specialist spaces. We are adding the smaller HEPA filters to these locations based on those changes.

What about larger rooms:

Some sites are using larger rooms for programs to increase distancing. Those rooms would require a significant amount of filters to address that large air volume. Therefore, we are not placing the portable units in the large spaces. Additionally, the large spaces are more closely approaching an outdoor environment due to the still small cohorts in the larger volume of air. Back to the pool analogy. It's like someone peeing in a lake vs someone peeing in the above ground pool.

Where should the portable filter be placed in the room:

We've defaulted to putting it near the front of the room under the assumption that is where the teacher will teach from in this new environment. It doesn't really because the filter cleans all the air in the room but it cleans the air around it first.
In many rooms, the front is not feasible. It is fine to put it at the back of the room. The large filters are intended to filter the air in the entire room.

What about the isolation room:

We are not putting any additional filtration in those rooms since we hope to not need to use them
We have sealed off the return air in the isolation room on every campus. That means the air will not recirculate anywhere in the rest of the system. Those rooms are essentially sealed off from any other systems.
When those rooms are used, we will follow a safety protocol to clean and sterilize those rooms.

Do I leave my unit on every night:

Currently the engineers recommend leaving them on at least 2 hours before and after occupancy. Therefore, go ahead and leave them on each day. Again, we'll deal with the added energy used when we get through this. Also, the energy use of the filters is significantly less than air conditioning so we'd rather have the safer room air.

Can I turn them off:

Yes, but we don't recommend it. There is a switch on the back of the unit. If you want to turn it off, before or after students are in the room, flip the switch but you will then have to remember to turn it back on. We would recommend if you want to turn it off after a room full of students that you let it run at least 30 minutes to help clear out the air.
We do not advise turning them off when you have students because they are there specifically for the groups of people.
Additionally, if you have a substitute one day, they will not know to turn it on.

Can I turn off my Mechanical ventilation:

No. At the moment we have overridden room controls to provide continuous ventilation.
The current recommendations are to ventilate the rooms before and after they are occupied.
Normally, the ventilation only occurs when there are people in the room so we have forced that on.

Will custodians turn the portable units on and off:

No. Their time is critically spent on the disinfecting they are doing every night.

Will I have my portable filter all year:

Probably not. Our goal is to continue our pass/ fail testing of the ventilation in the rooms and once a room passes we will remove the portable unit and move it to another area that needs it like the 2/3 grades then the 4/5s and then the middle and high schools. After we've caught up with all the mechanical unit testing, we think the portable ones will remain deployed in rooms that do not have mechanical ventilation.

Will the District change the filters on the portable units:

Yes, part of the benefit of these are they are standardized and use commercial filters that are easy to acquire. Filters have become one of the hardest things to acquire right now, like toilet paper in March, so having a standard size makes it a lot easier to change and we will do so when we change our built in units.

Why are the portable filters so large:

They are commercial grade and are sized to meet the needs of a classroom. If you looks at a classroom's HVAC unit, they are this size or larger. To really meet the needs of the space, you need a large unit.

Noise

Will my Mechanical ventilation be more noisy:

A little bit. We've increased the outside air volume and locked the units to continuously provide air. So it will be a little noisier than it used to be. Not a lot, but a little.

The portable units are really noisy:

Yes. We know this. These are the quietest ones we could get that do what they do.
They are 59 decibels which is similar to conversation.
It takes a lot of force to push air through a HEPA filter. We weighed this issue and consciously chose to go forward with these units because we felt the benefits outweighed the noise.
Back to the item on room placement, if you feel the noise is reduced by putting it in the back of the room, that will work as well.

Why is the mechanical ventilation quieter than the portable ventilation:

The main reason is the duct size and the HEPA filter.
We have large ducts and large registers to supply air from the classroom units to the classroom space. One of the primary jobs of a Mechanical engineer is to design systems with a minimal noise as possible.
The HEPA filter is like pushing air through a wall. It takes a lot of force to do so.

Can you turn the noise down:

Yes, but only a little. That also turns down the filtration rate. In most cases we've already turned them down as much as we can.

Why didn't you buy a quieter model:

We did a lot of research. These are commercial grade filters which produce a lot of filtered air to help keep you safe.
Some other Districts bought units that cleaned at a quarter the rate but were 70 decibels.
The vendor did a test with all their available portable units and found the unit we purchased produced more filtration and was quieter than the other commercial grade ones.
This portable unit also has the ability to add bipolar ionization which we believe will be an additional added bonus.

Bad Air Quality/ Smoke

What do I do now - open my windows for COVID-19 or close them for smoke:

The best advice we have right now is still to close your doors and windows to keep out the bad air.
That advice contradicts with the more airflow goals for COVID-19

Mechanical ventilation smoke guidelines:

If you have mechanical ventilation, close your doors and windows. There is already sufficient outside air and it will recirculate through the filter.
Due to the filter recirculation, the indoor air will always be cleaner than the outside air
We are adjusting our controls to more quickly be able to close some of the outside air to more finely tune these reactions.

Portable filter guidelines:

Your portable filter will also do a good job of filtering the smoke. Here is a video showing the effectiveness of the filters in a smoke filled room: https://www.priceindustries.com/resources/videoplayer/3998

Is there anything else you can do:

The Superintendent's office continues to monitor the air quality daily to determine if the AQI will be over 150 the following day. We are continuing to seek out further solutions and data to provide better recommendations.
As part of our bipolar ionization testing, we have a testing company lined up to come the next time we have a smoke day to do specific smoke samples. We missed the smoke days this fall for this testing but will be prepared if there is another smoke event so we have better direction.
We will test smoke specifically in standard rooms, bipolar ionization rooms, portable filtered rooms, and outside.

Will the District change any of these directions:

Maybe. Probably. It seems that change is the only thing we can count on these days. Let's get back to school and then look at adjusting. For the moment, we are erring on the side of caution to make our rooms safer. In the long run, we will continue to make tweaks and continue to learn more about the transmission of the virus. When we make an operational change we will let you know.

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