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The CAB is a public database that contains information on the ventilation performance of actual facilities. It is closely integrated with the ACH Calculations Tool (ACT) which allows users to quickly enter data to calculate the ventilation performance levels in the rooms in a facility and save it in the public Air Changes Per Hour (ACH) database. So there are 2 databases, the CAB which sumarizes the ventilation of a building and the ACH which has all the room details. The intent of this database is to build awareness on the importance of Clean Air in all our facilities and realize that ventilation is about ACH levels and that the ACH levels in all our buildings must be disclosed.
Everyone is encouraged to add facilities into the CAB and ACH databases especially the general public. If you add your facility, you can print and post the Clear Air Building Certificate showing your occupants that you care about the ventilation in your facility. Anyone can add a facility. Just make sure you have reasonable data before you print and post the certificate.
These are ventilation education links:
This is the ACH database link: ACH Calculations Tool
The Facility Ventilation Reporting service allows users to fully navigate through the entire CAB and ACH databases. Visiting a facility, check out the ventilation. If there is no data, enter it using this service. There is also a Smartphone FVR version.
Website Facility Ventilation Reporting
Check or Add a building, airplane, train, or bus. |
A building ventilation system
is a life support system.
If the ventilation is not
working properly people will be infected by airborne contagions.
Ventilation performance is
key to ensure that the risk of infection is minimized or eliminated in a
room.
Ventilation is measured in
terms of Air Changes per Hour or ACH.
If the ACH is zero people
will be infected by an airborne contagion.
As the ACH level increases
the risk of infection drops.
For hospital rooms with airborne
contagions the CDC recommends a minimum of 12 ACH.
The Heating Ventilation and
Cooling (HVAC) systems and UV systems are the primary approaches used to
ventilate buildings.
Many buildings have
poor maintenance with closed off vents, failed fans, or poor operations where
the system is turned off when people are present.
Many buildings have
systems that are too small.
The Facility Ventilation
Reporting APP allows people to take control of their environments and examine
the ventilation rates of the buildings that they visit.
Anyone can add buildings
to the database if there is no data.
The CAB data is a summary
of a facility.
The ACH data has multiple
rooms found in a facility.
When there is real time data
available from the building, it is reported and available from the FVR APP.
Learn More: Building Ventilation
How can I do this: Ventilation Site Survey
Where to find data: Finding Facility Data
Example Reports: LAX Los Angeles International Airport . Hawaiian Airlines . Airplane 767-300 . Philadelphia Restaurant Program
Example Certificate
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The COVID-19 disaster has exposed the importance of clean air within buildings. The guidance throughout the disaster has been for building owner operators to check their ventilation systems and if needed perform reasonable improvements. Many building owners and operators have been proactive and they have taken the guidance seriously and improved their ventilation systems.
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.
COVID-variants may be with us for years to come, and this will certainly not be the last respiratory virus pandemic. We have long suffered from annual contagious respiratory infections, but exceptionally low rates of influenza and common colds during COVID-precautions have demonstrated that not all of this suffering need happen. So, we need to think clearly and scientifically about how better we can reduce the spread of viruses indoors especially when and where masks will no longer be in common use.
Are there effective engineering controls that can help make indoor environments truly safer?
Yes, the purpose of this piece is to emphasize the importance of focusing on air disinfection in the rooms where person to person aerosol transmission is occurring.
Buildings must comply with local building codes and many assume that establishes the ventilation performance requirements that must be met. However, that is an incorrect assumption. The building codes only establish the minimum ventilation requirements that must be met and buildings can exceed those minimum ventilation performance requirements. The other issue is the building codes do not represent what is needed for airborne contagions except for hospitals. So elite buildings will have great ventilation equal to or exceeding hospital ventilation performance levels.
Some buildings exceed the minimum ventilation performance requirements and they are buildings that were built in the 1920's, 30's, 40', 50's and 60's that were retrofitted with HVAC systems. Their performance levels are high and they exceed local building codes. There are also newer buildings that exceed local building codes with very high levels of ventilation performance requirements and they are elite buildings.
When the energy crisis happened in the last century, there was a massive push to reduce energy consumption and this resulted in significantly reduced ventilation levels. With the rise of sustainability in this century there is an additional push to reduce energy consumption and this is resulting in a further push to reduce ventilation in buildings. Many are now advocating that a building ventilation system just provide enough ventilation to prevent CO2 poisoning. It is known that just maintaining the CO2 levels is an extremely low level of ventilation where airborne contagions will make people sick.
Currently there is a battle behind the scenes between engineers and scientists that want proper ventilation performance requirements placed into all building codes and those that are fighting this effort. Those that are fighting this effort are: (1) the building owners that quickly realized during the energy crisis in the last century that they could save significant amounts of money and (2) those pushing for reduced energy consumption to reduce the effects of global warming. Those pushing for reduced energy consumption have impacted local building codes and now older buildings with high ventilation performance levels are being forced to lower their ventilation system performance levels. This is a serious battle and it is a challenge for this generation in this century.
A building ventilation system is a life support system and if it does not work properly people will be harmed.
It is clear that COVID-19 is spread by inhaled aerosols. Outdoors, dilution of aerosols are infinite although the time it takes to dilute clouds of aerosol depends on air movement. Imagine how a cloud of cigarette smoke lingers or dissipates depending on whether there is a breeze. Indoors, aerosols linger much longer than outdoors, often long enough to be inhaled by someone sharing the same space. If you breath in an indoor setting where other people are also breathing, if the ventilation is poor, you will breath in some of the air that someone else exhaled.
Ventilation is the way that the risk of indoor airborne infection is reduced.
One ACH (air change per hour) happens when a volume of air equal to that of the room enters and leaves over a period of one hour. For hospital procedure rooms, the CDC recommends 6 to 15 ACH with infection free outdoor air, or air that has been filtered or decontaminated. For rooms with airborne contagions the CDC recommendation is 12 ACH. We know that people will be infected in rooms where the ventilation is 0 or 1 ACH. We also know most existing ventilation systems are on demand systems, which means there is no ventilation (0 ACH) until the system turns on to either cool or heat a room. Most systems have a fan mode but no one is turning on the fan mode on these systems. We also know that most systems are sized to be 4 ACH which is a marginal ventilation performance level.
The CAB is a result of research on COVID-19 from a systems perspective that began in March 2020. The findings are summarized as follows:
There is more information at the following links:
If you are a facility owner or operator, ask your HVAC company to provide you with the data. If you plan to visit a facility, you can use the Internet to try and find the ventilation data for the facility you plan to visit. If you are already in a facility, you can do a rough assessment and gather data using observations. It is amazing how accurate this broad assessment of a facility without tools can be and it is a very reasonable source of data. Keep in mind that when the term facility is used this includes airplanes, trains, and busses.
There are 2 types of ventilation: Natural Ventilation and Mechanical Ventilation. Natural ventilation could be augmented with mechanical ventilation. For example in a resort setting a restaurant may have massive natural ventilation and it may be augmented with a mechanical HVAC system to add cooling or heat as needed for comfort.
Natural Ventilation
Natural ventilation is accomplished with open windows and doors. The following are some guidelines to estimate the ACH for natural ventilation. The following ACH estimates come from the WHO in a document on natural ventilation; Estimated air changes per hour and ventilation rate for a 7 m X 6 m X 3 m ward.
| Openings | ACH |
Ventilation rate |
| Open window (100%) + open door | 37 |
1300 |
| Open window (50%) + open door | 28 |
975 |
| Open window (100%) + closed door | 4.2 |
150 |
The natural ventilation also can be estimated by treating the open area to the outside as a vent and estimating the Feet Per Minute of air movement through the opening. That estimate can be accomplished using the methods for mechanical systems described further in this procedure. These estimates can easily approach 60 ACH when large entry ways are left open to allow for massive natural ventilation.
Outside ventilation is a form of massive natural ventilation and ACH estimates can range from 60 to 120+ ACH depending on the wind speed. A wind speed of 1 mile per hour will move 5,280 Feet Per Hour of air past a person. This is 5,000+ ACH assuming a person is breathing within a 1 cubic foot space around the head. Even if they are in the direct trajectory path of an infected person, it is unlikely that the infected air will have sufficient concentration to cause any issues unless they are directly talking at the person with no ability to dilute and disrupt the infection cloud. Crowds are a scenario where this infection route may surface. Court yards will have blocked airflow but unless their is a roof like structure, it is very unlikely that low ACH levels will surface.
Based on the above discussion the following ACH levels can be applied to the following Natural Ventilation scenarios.
| Natural Ventilation Scenario |
ACH |
ACH |
Comments |
| Open Windows | 4.2 |
4.2 |
WHO Natural Ventilation for Infection Control in Health-Care Settings |
| Open Windows and Doors | 28 |
37 |
WHO Natural Ventilation for Infection Control in Health-Care Settings |
| Open Entry | 37 |
60 |
Observations 4 X 8 ft entry, 300 Feet Per Minute, 1200 sq-ft, 8ft height |
| Open Walls | 60 |
120 |
Conservative outside ventilation assumption, 0.02 MPH wind max |
| Patio | 37 |
120 |
Conservative outside ventilation assumption, 0.02 MPH wind max |
| Outside Unblocked | 60 |
120 |
Conservative outside ventilation assumption, 0.02 MPH wind max |
| Outside Courtyard | 37 |
120 |
Conservative outside ventilation assumption, 0.02 MPH wind max |
| Outside Massive Crowds | 0 |
4 |
Ventilation ineffective due to close distances and blockage from crowd |
Mechanical Ventilation
The following is a procedure used to gather data and calculate the ACH in a facility using mechanical ventilation without using room size and anemometer measurements. This is called seat of the pants analysis but it is amazing how close the results will match results using tape measures for room sizes and an anemometer.
When you get home or to the office you can make the calculations. The following steps are used to make the calculations.
The following is an example to estimate the facility size and calculate the square feet and cubic feet. [facility-calculations] spreadsheet.
The CAB has its own mechanism to capture the facility data and calculate the ACH. It is available at Add A New Facility. There is a link on the form near the ACH entry areas called ACH Calculations.
| Item |
Data and |
Comment |
| Room length ft | 64 |
16 4 foot windows 16 X 4 |
| Room width ft | 30 |
10 3 foot windows 10 X 3 |
| . |
|
|
| Room sq feet | 1920 |
sq feet = Length x Width |
| . | . |
. |
| Room height ft | 20 |
Estimated as 2 10 foot sections |
| . | . |
. |
| Room cubic feet | 38400 |
cubic feet = sq feet X height ft |
The following is an example to calculate the ACH in a facility.
| Item | vent type A | vent type B | Comments |
| Vent length inches | 3 |
12 |
|
| Vent width inches | 36 |
36 |
|
| number of vents | 6 |
9 |
|
| Vent sq inches | 648 |
3888 |
Vent sq inches = Length X Width inches |
| Vent sq feet | 4.5 |
27 |
Vent sq feet = Vent sq inches / 144 |
| air ft per min (measured or estimated) |
200 |
200 |
measured air ft per min comes from an anemometer measurement. estimated air ft per min comes from the general rules:
|
| cubic feet per min CFM | 900 |
5400 |
CFM = Vent sq feet X air ft per min |
| cubic feet per hour CFH | 54000 |
324000 |
CFH = CFM * 60 |
| total CFH | - |
378000 |
total CFH = add all the vent types CFH |
| . | . |
. |
. |
| ACH | 9.8 |
|
ACH = total CFH / Facility cubic feet from previous table that calculated facility size. Do this for the min, max, and avg ACH. |
Use the [facility-calculations] spreadsheet or the CAB ACH Calculations to make calculations.
Based on the data you collected and the calculations performed you should have all the data to make a facility entry. Use the comments area to add all your observations and data that you collected. The comments will appear in the Clean Air Building certificate.
The following tables list differnt vent, diffuser, and return grill sizes that can be used to estimate the size of the vents in a facility.
Vent, Diffuser, and Return Grill Sizes
When looking at a vent, diffuser, or return grill the outside size is larger than the actual vent opening. The following tables identify the vent, diffuser, and return grill openings. The vent, diffuser, and return grill size exceeds the opening on each side by 1 inch. So a vent that looks like and measures from the outside as a 4 x 12 inch vent is really a 2 x 10 inch vent because that is the size of the opening. Also, the opening might be partially blocked around the perimeter and with reinforced strips down the middle. So a 4 x 10 vent might scale down to a 3 x 8 vent opening.
Vents
If applicable pick a vent size and enter it in the ACH Calculations table (Length and Width). Keep in mind the FPM level for when the Vent Air FPM is requested.
Vent Sizes
Note: Most likely near 350 FPM |
Diffusers
The following tables are vent diffusers. and they show sizes and typical airflow. When the CFM is divided by the area of the vent this provides the FPM.
This can be used as a guide when making observations or actually measuring the vent FPM.
The FPM numbers in the table are the upper limit and the airflow will Most likely be near 350 FPM.
If applicable pick a Diffuser size and enter the neck diameter in the ACH Calculations table (Width / Diameter column). Keep in mind the FPM level for when the Vent Air FPM is requested.
4-Way Diffuser Sizes
Note: Most likely near 350 FPM Round Diffusers
Neck Sizes are: 8, 10, 12, 14 inches Note: Most likely near 350 FPM |
Linear Diffuser Sizes
Note 1: 50mm/slot or 1.95 inches/slot |
The following table can be used to deal will mixed sized vents in a room.
Neck Size (in) |
Area sq-in |
6 |
28 |
8 |
50 |
10 |
79 |
12 |
113 |
Return Grills
You can measure the ventilation level using the vents / diffusers or return grills. The return grills suck in the air, send it through the system, and then expels the air out the vents / diffusers. Measuring the return grills will provide an indication of the percent of outside air being introduced into the space. It is also a good sanity check of the vent diffuser measurements.
The following are return air grills. The return air grills are similar in size to vents. The data in the following tables are based on 350 linear feet per minute (FPM) as measured at the grill.
If applicable pick a vent size and enter it in the ACH Calculations table (Length and Width).
Horizontal Return Air Grilles
Note: Most likely near 350 FPM |
Square Return Air Grilles
Note: Most likely near 350 FPM |
Verticle Return Air Grilles
Note: Most likely near 350 FPM |
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.
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.
There is great resistance on the part of facility managers to perform ventilation measurements and disclose the ventilation rates in terms of ACH. Others still appear to be trying to determine how to proceed. The following procedure is offered to volunteers to gather ventilation data. This can be performed by parents, teachers, unions, residents, employees, owners, and others for schools, clubhouses, libraries, workplaces, buildings of all types, transportation vehicles of all types, and other spaces.
Staff - 3 people
Tools
Calculations
You can use the ACH Calculations Tool (ACT) or perform the calculations yourself as follows:
Reference Data
Test Procedure
Cubical Area
Rooms
Hall
Bathrooms and Snack Room
General Guidelines
Embeded video link https://www.youtube.com/watch?v=HlneLDi9r54 (video on how to calculate air changes per hour)
If you can't measure the ventilation rates from the vents then just count the number of vents and use the guidelines at the start of this page to determine the ventilation rate from each vent. Pick the vent size and estimate the ventilation rate. If you feel air across your face the facility ventilation is not bad. In the calculations you can assume 100, 200, 300, 400 linear feet per minute per vent. If you don't feel air across your face you can assume 0, 50, 150, and 200 linear feet per minute. See section Finding Facility Data.
The procedure and process is very simple. Do not be side tracked with irrelevant details that some may claim to stop the measurements. Just roll up your sleeves and do the work and then present it to the community.
Copyright © 2021 Cassbeth Inc. All Rights Reserved. Proprietary. This information can be only used for education, research, or news media organizations. Any other use of this information by any entity where there is a financial transaction such as for products or services by for profit, nonprofit, and government organizations must contact Cassbeth for release. |
