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F V S E - Facility Ventilation Search Engine

In 2022 this research focused on how to educate people on ventilation and the development of tools to help capture, document, and understand a facilities ventilation performance levels.

Once people are educated and the tools are provided, the key challenge is how to get facilities to disclose their ventilation performance levels. The following template is provided that can be submitted to facility managers to request disclosure of ventilation performance levels in their buildings. It was developed from white papers that were requested by a very large organization to help them address this critical need. (do not click the link yet, keep reading)

embedded video


There is a presentation that attempts to address the education challenge. The goal is to provide a general presentation that can be distributed everywhere to stimulate building ventilation discussions that are based on performance numbers and the full disclosure of the ventilation performance numbers within buildings. (do not click the link yet, keep reading)

There is an earlier generic presentation. There were different versions of this presentation.

The ACH Calculations Tool (ACT) allows users to capture the Air Changes Per Hour (ACH) of rooms in a building. This seems like a trivial exercise until one attempts to capture this data. It is about the human factors interface to allow for fast and easy entry of data. This is a third generation attempt to create a user friendly mechanism to capture ACH performance levels. It is integrated with the Clean Air Buildings (CAB) database that allows users to print room and building level certificates. (do not click the link yet, keep reading)

Clean Air Buildings (CAB) was developed to allow anyone to capture the ACH of rooms in a building and post it in a public database. The public database also allows users to search for buildings and examine the ACH performance levels. The goal is to just assess buildings for their current conditions but not make any judgments of risk. (do not click the link yet, keep reading)

Learn more:

Building Ventilation Logos: Copy and paste to your emails.

Building Ventilation

Building Ventilation

Building Ventilation In The Age Of Contagions

Why is Ventilation Suddenly a Problem

Professor Edward A. Nardell Harvard Medical School

From Time Magazine: If We're Going to Live With COVID-19, It's Time to Clean Our Indoor Air Properly, Edward A. Nardell is Professor of Global Health and Social Medicine, Harvard Medical School.

A Paradigm Shift to Combat Indoor Respiratory Infection

In May of 2021, 39 scientists published "A Paradigm Shift to Combat Indoor Respiratory Infection"

There is great disparity in the way we think about and address different sources of environmental infection. Governments have for decades promulgated a large amount of legislation and invested heavily in food safety, sanitation, and drinking water for public health purposes. By contrast, airborne pathogens and respiratory infections, whether seasonal influenza or COVID-19, are addressed weakly, if at all, in terms of regulations, standards, and building design and operation, pertaining to the air we breathe.


Ventilation what is it?

ACH = Fan Cubic-feet per Hour / Room Cubic-feet

Ventilation what is it?

Example: 60 min / air changed every 3 min = 20 ACH

Scenarios Analyzed

Scenarios show probability of infection 99% to .0003%

What should be the ACH Level?

What have facility managers done?


What Must Happen

Facility managers should post their ventilation rates in terms of ACH in all spaces and as a summary for the whole building.

What is the future

Ventilation Approaches

What About The Home

What about costs?

Commercial Facility Costs

Where do ACH standards and guidelines come from?

Most of the ACH levels are based on comfort except for when airborne contagion mitigation is required in hospitals

ACH Standards & Guidelines




Source Area


Hospital Trauma room 15 - CDC Classroom (Art) 16 20 EPA
Hospital room airborne precautions 12 - CDC Malls 6 10 EPA
Hospital operating room 25 - Office 8 30 Greenheck
Hospital rooms 6 10 EPA Engine Room 20 60 Greenheck
Restaurants 8 12 EPA Kitchen 12 60 Greenheck
Restaurants 8 20 NCI Kitchen 7 8 NCI
Restaurants 15 20 wiki Kitchen 14 18 NCI
Bar 15 30 Greenheck Kitchens (commercial) 15 30 EPA
Bar 15 20 NCI Retail 6 10 NCI, wiki, EPA
Bar 15 20 wiki Laboratory 12 30 Greenheck
School Classroom 4 12 EPA Laboratory 6 12 wiki
Auditorium 8 15 EPA Club Houses 20 30 EPA
Assembly Hall 6 8 EPA Theatres 8 15 EPA

Commercial Building Challenges

It is more about proper maintenance and operation because this will lead to ACH = 0 or ACH = 1

Periodic inspections with documented evidence using certificates that are posted will ensure effective maintenance

Room / Zone Certificate Key Elements

Building Certificate Key Elements

Final Comments

Final Comments

It will take years for the building codes to change to include contagion mitigation, so what can we do?

As responsible managers of our children's future

Some Screen Shots

ACH Calculation Tool

Example ACH Calculations Entry

CAB Entries

Example CAB Entries

CAB Certificate

Example Certificate

Links & Contact

COVID-19 Research From A Systems Perspective

Walt's Bio

Healthy Infrastructure

The Philadelphia Art Museum and Water WorksThe Philadelphia Water Works was the first water treatment facility in the United States. It was a model for all future water works to follow in the New World. People would flock from around the planet to see this facility which combined engineering and art to solve a massive problem of safe water for the inhabitants of Philadelphia. It was born of necessity as the people decided they would not tolerate yet another yellow fever outbreak. The Museum sits on top of the original water reservoir that provided the city with water. As Philadelphia grew the reservoir and Water Works could no longer meet the needs of the city and new projects eventually replaced this once great technological and artistic achievement. It stopped operations in 1909.

A post vaccine world implies that everyone has received a vaccine against the COVID-19 virus. However, we know that will not happen. In the USA some will refuse the vaccine. In many countries the poor will not have access to the vaccine. The idea of a post vaccine world also suggests that we can return to the pre-COVID world. However, we know that is not the case. The contagion and its variants will be in the environment for decades. This is not unlike the situation that existed in the early part of the last century where there were deadly contagions that were part of normal life. It was not until multiple technologies were introduced in multiple systems that there was a decline in many deadly contagions in the USA and other parts of the world. These technologies and systems were embedded in:

In the wake of the COVID-19 disaster the city of Philadelphia has once again taken lead actions like the Enhanced Ventilation Standards for Indoor Dining and Application Form for Increased Dining Capacity dated February 14, 2021. The Enhanced Ventilation Standard calls for 15 air changes per hour (ACH) for establishments wanting to double their seating capacity. The approach is brilliant and uses the incentive to increase income to offset any possible costs that may be needed to increase ventilation. The ventilation level increase is large and will significantly mitigate contagion levels in the restaurant. It is obvious that it is traceable to existing engineering requirements associated with contagions rather than subjective minimum comfort levels. As part of the initiative they posted howto videos:

https://www.youtube.com/watch?v=HlneLDi9r54 (video on how to calculate air changes per hour)
https://www.youtube.com/watch?v=58uRfAxh6Cw (video on how to complete the application)

These people are brilliant. The city of Philadelphia is leading the world on how to deal with the COVID-19 disaster for indoor settings. Unfortunately this program stopped in May 2021 leaving a void in this very important area of ensuring public buildings have ventilation levels that mitigate contagions rather than just provide minimum comfort levels. However, the model exists along with the recommended ACH level.

The city of Philadelphia has also taken the time and effort to understand their school facilities and they have performed an extensive site survey (air balance reports) of all their school. The school district has 240+ schools and 12,000+ rooms. They made this critical information public via their website. Once again Philadelphia has taken a lead in trying to deal with another aspect of the COVID-19 disaster and that is to understand the current state of the schools and share the data with the Philadelphia taxpayers and people everywhere.

How to Calculate Room ACH

There are 2 approaches to calculate Room ACH.

The first approach is to use the: ACH Calculations Tool - ACT. When you arrive at the page just press the ACH Calculations button and start entering data. This is probably the easiest approach. You also have the option of adding the building into the open source database of buildings around the world.

The second approach is to use the following steps to calculate the ACH for each room. Some rooms have multiple vents. Make sure to measure all the vents in a room.

  1. Measure room Length, Width, and Height in feet
  2. Measure each Vent Length and Width in inches
  3. Measure each vent Linear Feet Per Minute (LFM) using anemometer (buy the lowest cost ~ $19)
  4. Example anemometer: https://www.amazon.com/Anemometer-Handheld-Detector-Temperature-Windsurfing/dp/B07ZJ38ZMX
  5. Use the following steps to calculate the ACH
  6. Vent Cubic Feet Per Minute (CFM) = Vent 1 Length * Vent Width * LFM  1 / 144
  7. Room Ventilation CFM = Vent 1 + Vent 2 + ...
  8. Room cu-ft = Room Length * Width * Height
  9. ACH = Room Ventilation CFM / Room cu-ft

Write it all down so that you don't get lost. Use a separate sheet of paper for each room. Don't try to make perfect measurements. Room shapes are odd and ventilation readings vary. Set the meter to read the Max rate and move it across the entire vent. These approximate readings are all that are needed to make reasonable assessments of the ACH levels.

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