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The rapid development of air filters is closely related to the development of military industry and electronic industry. In the first world war, the use of various chemical agents, asbestos fibre filter paper as the smoke filter layer of military gas masks came into being. The glass fiber filter medium is used in air filtration to obtain a patent in the United States in October 1940. In the 1950s, the United States studied the production process of glass fiber filter paper, and the air filter was improved and developed. In the 1960s, HEPA filters came out; In the 1970s, the filter paper of fine glass fiber was used as the HEPA filter of filter medium, and the filtration efficiency of particle size of 013 micron particle diameter was 99.9998%. Since the eighty s, with the emergence of new test method, use evaluation to improve and to improve the filtering performance requirements, found the HEPA filter there is a serious problem, and he had a higher ULPA filter performance. Countries are still working on it and expect more advanced air filters soon
Timber French doors London If you plan on installing new doors you'll be able to imagine French doors made of timber. If you love old architectural styles then it is simple enough so that you can comprehend the relevance and depth of French doors. You may be apprehensive regarding how these doors will appear along with the rest of the furnishings. Take our word because of it ' these doors is only going to improve the attractiveness of your house, not diminish it at all. French doors make the room look bigger while offering great ventilation and natural lighting.
The inspection personnel of all kinds shall not exceed the scope of inspection and shall not engage in illegal punishment. The subject should be respected by the inspectors. The competent departments of the provincial departments shall carry out effective supervision and management of the inspection personnel of the system and find that the problems must be dealt with in a timely manner.
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