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.
This system does not share any air between rooms.
Air in your room stays in your room.
Windows do not open!
I was able to find the filter and its rating:
-MERV 6 (low efficiency)
- last changed = 9/20/21
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).
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 📦
Room did not have shared door with another adjacent rooms - did not use blue tape this time.
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).
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.
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).
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🧵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.
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.
@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.
📢📢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.
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
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
🧵 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?
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: