Experts have proved that activated carbon masks do not intercept PM2.5

In today's fast-evolving information age, a simple click can spread information across the internet in an instant. While it's easy to access, it also brings challenges with misinformation. From the "salt is useless" controversy to rumors about Beijing's water safety, various pseudo-scientific claims have flooded the web, sometimes confusing the public and even threatening social order. Since October, hazy days in Beijing have started to increase again, making masks a popular item. Many masks are advertised as effective against PM2.5. But which mask truly offers the best protection against fine particulate matter? To find out, a reporter recently invited experts to test the filtering performance of seven different types of masks. **Experiment** The most effective mask for blocking PM2.5 was the N95. The reporter purchased various masks including N95, non-woven, PM2.5-specific, activated carbon, cotton, 18-layer gauze, and surgical masks from online stores, markets, pharmacies, and hospitals. These were tested by chemistry professionals using a particle analyzer that meets national standards. Inside the lab, a device similar to an oscilloscope had a fixed mask holder and a fan to create negative pressure, pulling smoke through the mask. After passing through the mask, the smoke was measured by a laser dust meter, recording particles larger than 1 micrometer. Instead of using toner, the experiment used cigarette ash, which is closer in size to real PM2.5 particles. This setup, created by a middle school student under expert guidance, provided reliable results. Testing began with a non-woven mask. After lighting three incense sticks, the PM2.5 concentration rose to 600 μg/m³. Within 15 seconds, the smoke was drawn into the equipment, and after one minute, the reading was 495 μg/m³, showing poor filtration. The 18-layer gauze mask performed slightly better, with readings stabilizing at 465 μg/m³. Ordinary cotton and activated carbon masks showed worse results, with PM2.5 levels rising quickly. In contrast, the N95 and surgical masks significantly reduced the concentration, with readings as low as 13 μg/m³ and 41 μg/m³, respectively. Experts explained that N95 masks offer the best protection, while ordinary cotton masks are the least effective. Activated carbon masks may also release small particles if damaged. Surgical and N95 masks, though effective, can be uncomfortable due to limited breathability. Public health experts advised choosing masks based on exposure time and personal needs. For short outdoor trips, a highly efficient mask is ideal. For longer periods, a balance between filtration and breathability is important. Regardless of the mask type, it's crucial to ensure a tight fit and avoid facial movements that could create gaps. Some masks use special filter materials like Reynolds fibers or microfiltration technology. Three-dimensional designs, such as the "porcupine arch," help the mask fit better against the face, reducing gaps. In a survey, only 25% of pedestrians wore masks, mostly non-woven or activated carbon types. Most people didn’t know how to choose the right mask for PM2.5 protection, often relying on sales recommendations without understanding the science behind them. In conclusion, while masks can help protect against air pollution, proper selection and correct usage are essential for maximum effectiveness.

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