#AAAR2022, @IAQinGWN.

- Lots of reasons filtration is not optimal.
> energy cost
> too noisy
> filtration replacement cost

1/
- Trade offs between performance and runtime.

- Can they improve on the concentration threshold approach for running the portable filter?

-Unlikely to be universal threshold due to sensor and environment variability.

2/
- Made some modeled data sets of source and removal rates.

- The threshold value changes based on the sources in each apartment.
/3
- Running the air cleaner continuously will always reduce concentration the most.

- BUT you get a relatively small benefit from improvement from running it only when exceeding threshold values. Run times can be down as low as 10-50% with most of the benefit.
4/
- An adaptive air cleaner run time threshold could operate 7% of the time and get 60% of the benefit of running it continuously. (Interesting).

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More from @Poppendieck

Oct 6
#AAAR2022. Plenary: @IAQinGWN

- A story about filters....

- How to improve indoor air cleaner
1- Keep it dry
2- Source control
3- Ventilation
4- Air cleaning

- Filtration (air cleaning) has the shortest history. Only 50-100 years use in buildings.
1/
- ASHRAE standard 52.2 for filtration is only 23 years old.

- Measured CO2 and PM2.5 decay in a classroom that was supposed to be operated at 6 air changes per hour with ventilation and filtration. But it was actually at ~2 air change per hour.
2/
- Why does filtration fail to meet goals?

- Issue #1. Air has to get to the filter. For central heating homes the recirculating rate can range from 2-8 when the fan is on. BUT the fan can often only 20% of the time, with HUGE variation on the run time.
3/
Read 18 tweets
Oct 5
#AAAR2022. @SarahRHaines

- Indoor dust can be resuspended by human activity. Dust can be use as a tracer to determine the presence/absence of RNA (i.e. SARS-COV2).

1/
- Deployed indoor air cleaners in homes/classroom where people who COVID positive.

- In home cleaners placed in isolation room, outside and in the main living area. After 1-2 weeks dust was removed from filters => extracted => qPCR analysis.

2/
- Cool mist humidifiers were often used in homes/isolation rooms which greater decrease the flow rates of the air cleaners.

- Isolation rooms in homes had higher copy numbers.

- SARS-COV2 was detected in 2/7 deployed filters in classrooms/lunchrooms.
/3
Read 4 tweets
Oct 5
#AAAR2022. @LioraMael

- How do homes recover when impacted from wildfires.

- @LioraMael notes that her home burned down in the Marshall fire the day before she was to move in. #RealworldImpacts
1/
- Looked particulate matter in a house on the edge of the Marshall fire roughly one month after the fire.

- Cleaning activities increased the particle concentrations in the home.
2/
- Particle concentrations below 500 nm increased both with cleaning activity AND when no one was in the house.

- 500 nm and below particle burst coincide with the HVAC cycles. Cause unknown.
3/
Read 4 tweets
Oct 5
#AAAR2022. Xiaochen Tang.

- Does long term exposure of Tobacco Specific Nitrosamines (TSNAs) lead to negative health impacts.

- Previous research shows TSNAs stick to surfaces. TSNAs hard to measure due to reactivity (esp NNN, NNK).
1/
- Added HONO enriched air to chamber with cloth coated with nicotine to create TSNA. Examined cellulose and cotton with/without sweat and skin oil.
2/
- HONO deposition increase with nicotine addition.
HONO deposition may have been inhibited by water presence in cotton materials.

-TSNA increased in production in present of sweat and skin oil.

3/
Read 4 tweets
Oct 4
#AAAR2022. @ProfPeteD. ALPACA Project Overview

- ALPACA - Investigation in artic air quality in urban artic environments.

- When it is -14F(?C) people are inside. But in Fairbanks there is a high prevalence of wood burning stoves.

1/
- What happens when you move polluted air from outdoors indoors with a 50 C temperature difference?

- In general outdoor PM10 concentrations higher outdoors than indoors, EXCEPT when pellet stove was used inside the house. 2/
- Furfural and furan, gases from wood combustion, had similar concentration indoors and outdoors. But outdoors had more variability.

- Cold outdoors most SVOCs are in the particle phase. Warm indoors the chemicals move into the gas phase.

3/
Read 4 tweets
Oct 4
#AAAR2022. @etgall

- Can you use consumer grade sensors be used to estimate particle infiltration.

- Survey asking what mitigation method they used during wildfires: main response stay indoors and keep windows and doors shut.
1/
- Corrected Purple Air sensor measurements to reference station.

- Outdoor PM2.5 concentrations varied by over a factor of 2 outdoors over 25 km during wildfire.

- Indoor concentrations varied from equal to outdoor data to order of magnitude lower than outdoor.
2/
- If you assume indoor sources are ignored, then you can use a mass balance to determine the infiltration factor.

- Assumption is better during night time (less human activity).
3/
Read 4 tweets

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