Junior high school composition 400 words "The weather suddenly turned cold"

It has entered 65438+February, but the weather has not turned cold. This morning, "Huhu", a north wind blew, and a few yellow leaves fell on the thin kapok tree soaked by the drizzle in Mao Mao. The kapok tree looked up feebly and looked at the few leaves left on her body, and could not help but shed tears sadly. Another cold wind came, and the kapok tree shivered and suddenly looked up and saw that everything had changed. Changed, changed, the hot pot city is steaming. In order to avoid the sudden cold, people gather here to taste wine and delicacies. Changed, changed. In front of the winter clothes counters in major shopping malls such as Wangfujing and Xindaxin, there are a sea of people. Warm items such as down jackets, electric blankets and electric heaters were snapped up. Changed, changed, the street, people are curled up, it seems shorter than usual. I saw a little girl wearing a dark brown plush coat, a tall beige screw cap on her head, and four fingers together, just like a little brown bear. As she walked, she said, "It's really cold! It's so cold! " Kapok tree was surprised to find that the breath exhaled by the little girl's mouth was clearly visible. At this time, the kapok tree saw the distant fields dressed in green vegetables singing heartily, and people's faces showed warm smiles in the cold, as if they were still immersed in the joy of "bidding for the Olympic Games", "Ninth National Games" and "joining the WTO". At this time, the kapok tree also smiled happily. Fog is water vapor and haze is dust particles. Inhalation will affect respiratory mucosa. Wearing a mask in foggy days, especially for professional medical use, can reduce dust inhalation and ensure respiratory health. The United States imported Puwei Xintianmao.

Buy anti-fog masks, one can look at the standard, and the other can look at the filtration efficiency.

Speaking of standards, people are most familiar with the N90 and N95 series masks of 3X brand, both of which are named after NIOSH standard. In addition to NIOSH standard, ASTM standard of American Society for Testing Materials, KN standard of China and FFP standard of Europe are all universal and can be used to measure important indicators of masks.

Among the indicators of masks, everyone is most concerned about the filtration efficiency of particulate matter. Therefore, before purchasing masks, you can learn more about the particle filtration efficiency corresponding to various standards. "N95" in NIOSH means that the filtration efficiency of particles as small as 0.3 micron reaches 95%. In fact, the highest standards of ASTM and FFP require higher particle filtration efficiency than NIOSH N95. For example, the ASTM standard requires a filtration efficiency of 98% for particles as small as 0. 1 micron.