Ventilation air,
Ventilation air,
Where are you?

🧵 Hotel and COVID-19 part 2.

You can find Part 1 here 👇 (still waiting for lab results - 1 more week).
@DavidElfstrom
This week, I stayed at an hotel and this time I came prepared.

Here are some observations about shared air, system type, filtration, and outside air rates.
Air conditioning system type = fan coil unit = fan + filter + cooling and heating coil.

➡️This system does not introduce any outside air. It only filter the air in the room by recirculating it through a filter then a coil then supplying back to the room. ImageImage
This system does not share any air between rooms.
Air in your room stays in your room.

Windows do not open! ImageImage
I was able to find the filter and its rating:
-MERV 6 (low efficiency)
- last changed = 9/20/21 ImageImageImage
Checked exhaust - only exhaust is from bathroom.
But the exhaust fan was not working! Measured 0 airflow.
(I reported the issue but they said it not something they can fix, only if I have issues with TV or AC). ImageImage
What about outside air (OA) supply to the room?
- no OA was supplied directly to the room
- no OA was supplied to the corridor

👇With no exhaust and no OA: meaning the room was a closed sealed box 📦 ImageImage
Room did not have shared door with another adjacent rooms - did not use blue tape this time. Image
Took CO2 measurements:
- CO2 values varied between 1000 ppm and 1200 ppm. 1 person in room.
- I did not measure while I was sleeping.
(Sensor = REED SD 9901, can log a large amount of data). Image
I double checked what the hotel policy on COVID-19. It was about PPE, cleaning and desinfection, and remote check in.

No mention of ventilation or filtration.

In room, there was a tiny complimentary hand wipes. ImageImageImage
Luckily I came prepared. I brought my desk small Levoit and turned it on high.
CADR = 140 CFM.

(Was inconvenient to bring it but Southwest airlines allows checked in bag for free). ImageImage

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More from @marwa_zaatari

Oct 14, 2021
🧵The search for ventilation.
Hotel & COVID-19 Edition.

I stayed yesterday at brand name hotel. Here are some observations about shared air, outdoor air, and maintenance issues.
The room I stayed in does not have shared air. This is typical for hotel rooms. Air in your room gets recirculated and conditioned within your room only - by design.

Pic for unit in my room: window unit with fan and cooling/heating coil. Image
Indoor air gets recirculated on the side, conditioned and then blown from the top - as shown by my infrared camera. Blue = cold air. orange = "hot" air.
Hint: to know the intake of air on the unit, look where there is dust. Image
Read 12 tweets
Sep 27, 2021
@JudahWorldChamp @kprather88 @CorsIAQ @jljcolorado @HuffmanLabDU @Poppendieck Hotels do not have shared air by design with 1 caveat.
- In your room, you will have a unit that circulates and conditions only your room air (not shared).
- This unit might be under a window, next to a window, or in corridor of your room next to the bathroom.

See pictures below
@JudahWorldChamp @kprather88 @CorsIAQ @jljcolorado @HuffmanLabDU @Poppendieck Typically, for outside air, hotels (like Hilton and Marriott) have an outside air unit on the roof that brings the air into the building.

So far so good.
Your room air is not shared air with other rooms.
@JudahWorldChamp @kprather88 @CorsIAQ @jljcolorado @HuffmanLabDU @Poppendieck There are two ways to get outside air to the room:
1- Supply outside air directly into the room. That is the preferred method. See picture below. You will see a diffuser above the ceiling, next to the bathroom.

If that is the case, your room is isolated from other rooms.
Read 6 tweets
Sep 18, 2021
📢📢New! Air Cleaners Comparison:
1- Selection graph: 1.a. all + 1.b. only HEPA
2- Data download link
3- Request data link
4- Where to place air cleaner?
5- Calculate reqs
6- CADR and noise
7- Letter about unproven tech.

@CleanAirCrewOrg @DavidElfstrom
@kprather88
1a - Selection Graph - All (includes ionizers = unproven tech)
- X axis first cost + first year filter replacement cost in USD
- Y axis: Clean Air Delivery rate = volume of clean air in CFM (cubic feet per min) = ~efficiency x airflow Image
1b - Selection Graph - only includes HEPA
- X axis first cost + first year filter replacement cost in USD
- Y axis: Clean Air Delivery rate = volume of clean air in CFM (cubic feet per min) = ~efficiency x airflow

Fun Fact:
On average, for each 1 cfm of clean air you pay $1.8 Image
Read 10 tweets
Aug 25, 2021
🧵 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
Aug 23, 2021
📢📢📢 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
Aug 20, 2021
🧵 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

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