Translating a novel wildfire smoke exposure chamber system from lab-based experiments to community-engaged activities

This paper describes the development and application of a low-cost, portable wildfire smoke exposure chamber system that enables the quantitative evaluation of DIY air filtration efficiency and facilitates community-engaged demonstrations, such as a successful live experiment conducted with a tribal community in Central Washington.

The Gist

The Big Idea: Bringing the Lab to the Living Room (and the Tent)

Imagine you have a super-accurate, million-dollar air quality testing machine. It's like a NASA-grade weather station for smoke. It tells you exactly how well an air filter works, but it's too heavy, too expensive, and too complicated to take to a town hall meeting or a community fair.

This paper is about a team of researchers who said, "What if we built a portable, low-cost version of that NASA station that fits in a pickup truck?" They wanted to prove that you don't need a fancy lab to show people that a homemade air filter actually works.

The Problem: Wildfire Smoke is a Sneaky Invader

Wildfire smoke is like an invisible, toxic fog that creeps into our homes. It's full of tiny, dangerous dust particles (called PM2.5) that can hurt your lungs and heart.

The best defense is a Portable Air Cleaner (PAC). You can buy expensive ones, or you can build a "DIY Box Fan Filter" (a box fan with a MERV 13 filter taped to the back). These DIY versions are cheap and easy to build, but people often ask: "Does it actually work? Is it just a fan blowing dust around?"

The Solution: The "Smoke Tent"

The researchers built a portable exposure chamber. Think of it as a giant, airtight grow tent (the kind gardeners use for indoor plants).

• The Setup: They set up this tent in a lab, and later, in a community center parking lot.
• The Smoke: Instead of waiting for a real wildfire, they used a smoke gun (like the ones bartenders use to smoke cocktails) to puff a controlled amount of woodsmoke into the tent.
• The Test: They turned on the DIY box fan filter and watched to see how fast the smoke disappeared.

The "Race Against Time" Experiment

To measure how well the filter worked, they used a concept called CADR (Clean Air Delivery Rate).

The Analogy: Imagine the tent is a swimming pool full of muddy water (the smoke).

• Natural Decay: If you just leave the pool alone, the mud settles slowly over time (leaks and dust settling).
• The Filter: Now, imagine you turn on a giant pump (the DIY filter) that sucks the water out, cleans it, and puts it back in.
• The Result: The researchers measured how much faster the water became clear with the pump running compared to just sitting there.

They found that the DIY filter was a hero.

• On low speed, it cleaned the air at a rate of 92 cubic feet per minute.
• On high speed, it cleaned 145 cubic feet per minute.
• The Verdict: It worked almost as well as the expensive, store-bought air purifiers tested in high-tech labs.

The Community Event: "Show, Don't Just Tell"

The coolest part of the paper isn't just the numbers; it's how they used this tent at a community gathering for a Tribal Nation in Washington state.

Usually, scientists hand out pamphlets that say, "Air filters are good." But people often ignore pamphlets.
Instead, the team set up the Smoke Tent right there at the event.

1. The Demo: They invited community members to help puff the smoke into the tent.
2. The Visual: They connected a sensor to a laptop and projected a live graph on a screen.
   • The graph went UP when they added smoke.
   • The graph went DOWN dramatically when they turned on the DIY filter.
3. The Reaction: People saw the line drop in real-time. They could see the air getting clean. It wasn't a theory anymore; it was a visual magic trick.

Why This Matters

• Accessibility: You don't need a university lab to prove a point. A $300 tent and a laptop can do the job.
• Trust: When people see the data drop in real-time, they trust the science.
• Action: Because they saw the filter work, many people at the event took home a DIY box fan and filter to protect their families from future wildfires.

The Takeaway

This paper is a story about democratizing science. The researchers took a complex lab experiment, shrunk it down into a portable tent, and brought it to the people who need it most. They proved that a simple, cheap box fan can be a powerful shield against wildfire smoke, and they did it by letting the community watch the smoke disappear right before their eyes.

In short: They turned a boring science experiment into a live magic show that saved lives.

Technical Summary

1. Problem Statement

Wildfire smoke (WFS) events in the Pacific Northwest pose significant public health risks, exacerbating respiratory and cardiovascular conditions and causing long-term health disparities, particularly in rural and indigenous communities. While portable air cleaners (PACs), specifically low-cost Do-It-Yourself (DIY) box fan filters using MERV 13 filters, are effective mitigation strategies, there is a gap in how their efficacy is communicated to the public.

• Limitation of Current Standards: Standard testing for Clean Air Delivery Rate (CADR) relies on the Association of Home Appliance Manufacturers (AHAM) exposure chambers. These are expensive, non-portable, and confined to laboratory settings, making them inaccessible for community education and real-world demonstration.
• Need: There is a need for a low-cost, portable, and easy-to-assemble system that can replicate lab-grade particle removal experiments in community settings to visually demonstrate the efficacy of DIY air filters and promote behavioral change.

2. Methodology

The study employed a two-pronged approach: laboratory characterization of a DIY filter and a community-engaged live demonstration.

A. The Portable Exposure Chamber System

• Hardware: A commercially available 333 ft³ (9.43 m³) horticultural grow tent (VIVOSUN S105) was utilized. It features an Oxford canvas with a mylar inner layer and a metal frame. Openings were sealed with duct tape to minimize leakage.
• Particle Generation: Woodsmoke was generated using a food-grade smoke gun and woodchips, introduced into the tent via a sealed inlet port.
• Mixing: A pedestal fan inside the tent ensured uniform particle distribution.
• Instrumentation:
  • Reference: TSI 3330 Optical Particle Sizer (research-grade, sampling from outside the tent via a static-free tube).
  • Low-Cost Sensors: PurpleAir Classic (modified for 1-second logging) and Dylos DC1700 (connected to a laptop via serial port for real-time visualization).
• Experimental Protocol:
  1. Face Velocity Measurement: Measured using a hot-wire anemometer across a 3x3 grid on the fan face to calculate airflow (CFM).
  2. Decay Experiments: Woodsmoke was introduced to reach ~100 µg/m³. The system measured particle decay under "natural decay" (fan off) and with the DIY filter running at Low, Medium, and High speeds.
  3. Calculation: CADR was calculated using the decay constant method ($CADR = b_{box\_fan} \times V$), where $b_{box\_fan}$ is the net decay coefficient (experimental decay minus natural decay) and $V$ is the tent volume.

B. Community Engagement Event

• Context: A partnership with a tribal nonprofit in Central Washington (KHIMSTONIK) to distribute DIY box fan filters.
• Live Demonstration: The portable tent was set up outdoors. A modified Dylos DC1700 was connected to a laptop running R scripts to generate a real-time time-series plot of particle concentration.
• Procedure: Community members assisted in introducing smoke and observed the particle count drop when the filter was activated, providing a visual proof of concept.

3. Key Contributions

• Development of a Portable Exposure Chamber: Successfully adapted a commercial grow tent into a controlled environment for particle removal testing, offering a low-cost ($289.99 for the tent) alternative to the $100,000+ AHAM chambers.
• Validation of Low-Cost Sensors: Demonstrated that low-cost sensors (PurpleAir, Dylos), when properly calibrated or used for relative decay analysis, can yield CADR results comparable to research-grade instruments (TSI 3330).
• Translation of Science to Practice: Created a framework for "translating" complex laboratory data into interactive, visual community demonstrations. The use of real-time time-series visualization on a laptop was identified as a critical factor in engaging the public.
• Empirical Data on DIY Filters: Provided specific CADR data for a standard MERV 13 DIY box fan filter under controlled conditions.

4. Results

• Fan Characteristics: The DIY box fan (Lasko 20-inch) achieved face velocities of 55.5, 86.3, and 101.0 ft/min at Low, Medium, and High speeds, respectively.
• Airflow Rates: Calculated airflow was 741 cfm (Low), 1,150 cfm (Medium), and 1,350 cfm (High).
• CADR Performance (TSI 3330 Reference):
  • Low Speed: 92.2 cfm
  • Medium Speed: 129.9 cfm
  • High Speed: 145.2 cfm
• CADR Performance (PurpleAir Classic): Results were comparable, ranging from 79.2 cfm (Low) to 130.1 cfm (Medium), though slightly lower at High speed (116.1 cfm).
• Comparison to Literature: The results align closely with previous EPA studies on similar "baseline" DIY units, validating the tent chamber's accuracy.
• Community Impact: Approximately 15 attendees engaged deeply with the live demo. The visualization of the particle decay curve on the laptop screen was highly effective; attendees reported increased confidence in the utility of DIY filters and many took home units to use.

5. Significance and Implications

• Public Health Equity: This system democratizes air quality science, allowing researchers to bring rigorous testing capabilities to rural and indigenous communities that are disproportionately affected by wildfire smoke but lack access to university labs.
• Behavioral Change: The study confirms that "showing" (live visualization of particle decay) is more effective than "telling" (handouts) for promoting the adoption of air filtration strategies.
• Scalability: The low cost and modularity of the system allow public health agencies and community groups to replicate these demonstrations globally in areas prone to wildfire smoke.
• Limitations & Future Work: The authors note limitations regarding the consistency of woodsmoke generation and the sensitivity of the tent to extreme weather (rain/wind). Future iterations could utilize engineered dust sources (e.g., ASHRAE dust) for more consistent particle generation.

In conclusion, the paper successfully demonstrates that a low-cost, portable exposure chamber can effectively validate DIY air filtration efficacy and serve as a powerful tool for community science engagement and health education.