With air pollution making much difference to many of Chinese cities, parents are calling for the installation(安装) of air cleaners in classrooms. There has been much debate over whether air cleaners should be used in China's schools. Some parents have donated cleaners to their children's classrooms, while others raise money together to make the purchase(购买). “Our school bought air cleaners last year. We did a little fund raising, with each parent throwing in several hundred for that,” said one parent.

    However, the idea of installing air cleaners for all the classes has been refused by some schools. Liu Liangcheng, vice-principal of Beijing's Taipinglu Primary School, says installing air cleaners bought by parents may lead to problems. “We have refused air cleaners bought by parents before, as there are clear and strict rules against educational fees. We can't just break the rules here. And without standard guidance (指示) from local authorities(权威部门), it is hard to decide on the brand of the cleaner, installation and even safety of the device(设备).”

    Moreover, experts say air cleaners can cause other health problems. Deng Gaofeng who works for the China Academy of Building Research says. “ In the classroom, if we keep windows and doors closed, the concentrations (浓度) of CO₂ will double from 1,000 PPM to some 2,000 PPM. According to national safety standards, the highest level should not be more than 1,500.” In addition, experts say air cleaners on the market are mostly designed for homes or offices. Evaluation(评估) is needed to know whether they are suitable in classrooms.

    It seems whether air cleaners should enter China's schools is an ongoing question. It still requires a more detailed plan.

阅读以上信息，用恰当的单词完成下面的表格，每空一词。

Topic : Should air cleaners be installed for students in school?