单词:ultra-low-penetration air filter
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But the HEPA filter for Olivers Vibe got dirty very quickly. And, it was not cleanableit was simply replaceable. When it turned filthy brown, Oliver went back to Target to buy a new filter. Oddly, Target sold the F15 belt for the Vibe, but not the fi
From VOA Learning English, this is the Health Lifestyle report. In parts of India, it is not uncommon to see people wearing a mask over their nose and mouth. The capital, New Delhi, has some of the world's dirtiest air. The pollution was a call for a
By Cathy Majtenyi Nairobi 19 May 2008 Fuel efficient stoves and ceramic water purifiers are two examples of low-tech innovations that can help people in poor countries improve their quality of life. Because what is known as appropriate technology usu
By Tabinda Naeem Washington, D.C. 21 May 2007 Two years ago, the National Academy of Engineering established the Grainger Challenge Prize for Sustainability. This $1 million award was designed to challenge the world's scientists to develop a practica
Matt and his wife lived in the country. Matt was very stingy and hated spending money. One day a fair came to the nearby town. Let's go to the fair, Matt, his wife said. We haven't been anywhere for a long time.Matt thought about this for a while. He
今天我们要讲的习惯用语都有air这个词。大家都知道air是空气。早在十七世纪,意大利科学家伽利略发现空气似乎没有实质却有重量。后来人们进一步发现高山顶上的空气要比海平面上的空气