Share this page!

Maybe Scrolly?
Marwa Zaatari Profile picture
Twitter logo
15 Aug, 22 tweets, 11 min read
Updated 🧵Which air cleaner do I buy?

Type, efficiency, purchase price, replacement cost + filter life, and noise.

New results/charts about Intellipure DFS(TM), Blue Air(TM), and needle point bipolar ionization.

@DavidElfstrom @HuffmanLabDU @Parents4IAQ @RobynSchofield3
There are three types of air cleaners:
- Subtractive: like filters, will remove the contaminant when it comes in contact with the media
- Additive: like ionizers, will emit ozone/radicals/ROS/etc.. to react with the air (will emit something to remove something)
- Hybrid
Filter media (MERV, HEPA), UVGI are proven because Standards/guidelines/>decade of testing exist to test efficiency and by-products.

NO Standard exist today to test additive/electronic air cleaners (none, nada, zero, nul, nula), therefore they are Unproven.
Efficiency can be determined using the clean air delivery rate metric (CADR) = airflow of clean air.

For more info: ahamverifide.org/ahams-air-filt…
Rule of thumb: the CADR of your air cleaner should be equal to at least two-thirds of the room’s area to get ~5 ACH.
Selection chart of some air purifiers (option 1):
-Start by CADR (y-axis)
- Consider cost (x axis) – the lower the better. This is cost of purchase of unit + replacement of filter per year.
-Consider noise (look at color of the dot).
-Consider >1 cleaner to keep noise down.
Selection chart of some air purifiers (option 2):
-Start by area of room (y-axis)
- Consider cost (x axis) – the lower the better. This is cost of purchase of unit + replacement of filter per year.
-Consider noise (look at color of the dot)
-Consider >1 cleaner to keep noise down
If you are looking for purifiers in Australia/NZ, graph in $AUD here: @RobynSchofield3


Note: Corsi-Rosenthal box data will be added soon (I am missing the noise level!)
Don’t make the mistake of Dr. Fauci, make sure you are getting enough clean air for what you are paying for (expressed by x-axis $/ft2). You want high CADR with low cost and low noise.
For example, say that you have a room 400 ft2, you need an air cleaner with CADR ~ 250 CFM. See options in red circle.
Update: Blue Air (tm) purifier (1/3):
tweet:
New test data:built-envi.com/wp-content/upl…

Graph showing data with and without ionizer next.
Update: Blue Air (tm) purifier (2/3):

When you disable ionizer, the Blue Air purifier (fan and non-HEPA) decreases in performance. Take a look at the chart, much worse performance in terms of $/ft2 compared to other air cleaners. @smartrestartaps
(3/3)
Blue air (tm) purifier is a powerful ionizer and no-HEPA filtration. High level of ions has been shown to affect negatively cardiac markers (study done on college kids)
The impact on generating harmful gases (VOCs, formaldehyde) were not measured.
Slide by @ChemDelphine
Update: Intellipure (DFS) (tm) (1/2)
Old tweets:



New test data:
built-envi.com/wp-content/upl…

Graph showing data with Intellipure (tm) next.
Update: Intellipure (DFS) (tm) (2/2)

Look to the far right of the chart...not cost effective when compared to all other models on the chart... @Mssarahmssarah
Old but gold tweet about Sharper image purifier with CADR = 15 cfm:
Needle point ionization (1/3):

Graph here compares performance/cost of needle point ionizer versus HEPA filters. Not a good investment.
Needle point ionization (2/3):
Recent studies showed negligible effect on particle removal (field study in office as installed, field study classroom as installed, chamber study x 3, airplane x 2).

@linseymarr @built_envi
For additive/electronic air cleaners:
Studies showed potential by-product formation.
Morale of the tweet (1/3):
Choose only air cleaners that have mechanical filtration ( particulate filter media) with MERV 13 or higher or HEPA designation.
MERV 13 and HEPA are proven technologies, most are cost effective.
Be aware of false marketing:
HEPA-like
HEPA-style
99% HEPA
HEPAsilent (tm)
HEPA Ultra Ionic
HEPAFast
HEPA Efficiency
HEPA Function
HEPA Action
Plasma HEPA
Super HEPA
HyperHEPA
HEMPA
are ALL subpar versions of what constitutes a HEPA air filter. Either HEPA or NOT HEPA
Stay away of unproven technologies
Check the open letter for write-up and resources:
@MarcelHarmon1

medium.com/open-letter-to…

• • •

Missing some Tweet in this thread? You can try to force a refresh
　

Keep Current with Marwa Zaatari

Marwa Zaatari Profile picture

Stay in touch and get notified when new unrolls are available from this author!

Read all threads

This Thread may be Removed Anytime!

PDF

Twitter may remove this content at anytime! Save it as PDF for later use!

Try unrolling a thread yourself!

how to unroll video
  1. Follow @ThreadReaderApp to mention us!

  2. From a Twitter thread mention us with a keyword "unroll"
@threadreaderapp unroll

Practice here first or read more on our help page!

More from @marwa_zaatari

Marwa Zaatari Profile picture
25 Aug
🧵 Answers to what the different strategies will result in term of air change rate

Example used throughout the thread:
👉Classroom: 960 ft2: 30' x 32’
👉Number of occupants: 30 (this is the design number, taking into account average classroom density).
Ventilation by code, this classroom should have 415 CFM airflow of outside air or 14 CFM/person.

👉This airflow is being forced through the HVAC system (unit in classroom or mechanical room).
When we check ventilation, the answer is not “yes” or “no”, the answer should be how much?
Read 9 tweets
Marwa Zaatari Profile picture
23 Aug
📢📢📢 Updated Air Cleaner Chart:

I added the DIY CR box as optimized by @DavidElfstrom.

Look at this beauty!! @kprather88 @JimRosenthal4
It is the most cost effective purifier on the chart.

See below 🧵 comparison to intellipure(tm) /Blueair (tm)/needle point bp ionization Image
How it compares to Intellipure?
DIY CR/DE Box is 9 times cheaper and 2 times more effective and less noisy than Intellipure! @Mssarahmssarah Image
How it compares to Blue air?
DIY CR/DE Box is ~5 times cheaper and 1.55 times more effective than Blue Air 211+ @smartrestartaps Image
Read 4 tweets
Marwa Zaatari Profile picture
20 Aug
🧵 Is it enough?

"We did ventilation school assessment, we bought 2 air purifiers for each room for $40 million" "we conclude, it is safe to return."

A lot of time and money was spent. The school ventilation assessment is a great starting point, but what was the outcome?
Ventilation assessment reports can be found here: survey.nycsca.org/files/

I looked at many classrooms. Similar findings. Most do not have outside air and problems with exhaust fans of bathrooms (unless I am missing something - no reports it was fixed?).
Most schools have windows that can be open but windows are not a reliable method to get you a specific air change rate. For more information about ventilation:

Because mechanical ventilation is not available, a good option is to add air purifiers.
Read 7 tweets
Marwa Zaatari Profile picture
17 Aug
🧵Following-up: I did incognito testing at a famous casino last Aug. On my there, I felt uneasy - casinos were open and schools were closed.

However, this experience opened my eyes: if casinos can open safely and do it right, so can schools..

@HuffmanLabDU @DrEricDing
COVID Safety Plan (1/2)
- People density was at 50% (by design)
- Other measures below.
Everything was followed properly, except social distancing.

Masks were enforced, even outside. One might ask how can you enforce masks if people are drunk? I saw 2 people holding a person to his room while a third person holding by two fingers his mask in place.. commitment!
Read 7 tweets
Marwa Zaatari Profile picture
18 Apr
HVAC without V is a HAC(k) job

🧵 about ventilation
- Mechanical versus Natural ventilation
- ASHRAE Standard 62.1 historical rates
- Why schools are under-ventilated?
- What is the cost of outside air?
- What we should do about it?
Note 1: According to ASHRAE Standard 62.1 (most prominent ventilation standard), ventilation is not only about outside air. Rather, it is the sum of outside air and return air that is cleaned.

In this thread, I will focus only on outside air.
Note 2: schools are either designed to have mechanical ventilation (intentional OA from HVAC unit) or natural ventilation (intentional OA through windows and doors).

Most schools in North America are mechanically ventilated (for many reasons mainly for comfort and safety).
Read 16 tweets
Marwa Zaatari Profile picture
25 Mar
🧵about "Blueair" purifiers:

Consumer report rated this purifier as one of the best purifiers consumerreports.org/air-purifiers/…

1) Misleading marketing:
The filter used is called "HEPASilent". It is not a HEPA filter.
It is a common pleated filter + ionizer. ImageImage
2) By-products:
The company claim to produce low ozone.
It is certified by CARB to produce < 50 ppb.
They have a carbon filter which will capture some ozone - although % will decrease with use (we don't know how much % versus age).

Indoor ozone levels should be < 5 ppb Image
3) As we discussed previously, with every ionizer, there is a potential production of formaldehyde (and other VOCs) and ultrafine particles. Example of one ionizer tested by Lawrence Berkeley lab:

ww2.arb.ca.gov/sites/default/… Image
Read 5 tweets

Did Thread Reader help you today?

Support us! We are indie developers!

This site is made by just two indie developers on a laptop doing marketing, support and development! Read more about the story.

Become a Premium Member ($3/month or $30/year) and get exclusive features!

Become Premium

Too expensive? Make a small donation by buying us coffee ($5) or help with server cost ($10)

Donate via Paypal Become our Patreon

Thank you for your support!

Follow Us on Twitter!

Like this author's thread?

Get emails when @marwa_zaatari has new unrolls!

Check out other threads from @marwa_zaatari!

Read all threads by @marwa_zaatari

:(