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Freezing pollutants removes them from indoor air, study finds

Scientists have identified a new method of controlling indoor air pollution, which is capable of removing almost all pollutants simply by freezing them.

    Cars in traffic
    Hazardous outdoor air pollution severely affects indoor air quality

    An international study, involving Nottingham Trent University and the Chinese Academy of Sciences, aimed to address the severe effect that hazardous outdoor air pollution – which is thought to lead to more than 3m premature deaths worldwide every year – was having on indoor air quality.

    In cities with major air pollution, the outdoor air is often exchanged with the indoor air via windows and other openings.

    The research, led by Nottingham Trent University’s Professor Gang Pan, involved studying the effectiveness of cryogenics for indoor air purification, by removing the gaseous pollutants and tiny particulates caused by haze.

    The team found that as they circulated haze-polluted air through a cryogenic condenser, the finer particles stuck together in the condenser tube before dropping out by gravity, and emerging as clean air.

    Their method was able to remove 99% of particulates and 98% of nitrogen oxide pollutants.

    It is hoped that the work – which has a Chinese patent – could pave the way for simple modification of air conditioning and humidifier units so that they can have the option to clean polluted indoor air.

    “Hazardous outdoor air pollution has severely affected indoor air quality, threatening the health of billions of people,” said Professor Robert Mortimer, a researcher on the study and Dean of the School of Animal, Rural and Environmental Sciences at Nottingham Trent University.

    He said: “Outdoor air pollution in cities is a global problem, whether it be haze plaguing Beijing or poor air impacting the health of children in inner city London schools. While there are some existing technologies to purify indoor air, they can be inefficient, expensive or produce harmful by-products.

    “When outdoor air quality is poor, people tend to spend even more time indoors – but outdoor pollution also leads to indoor pollution and people are still impacted."

    Professor Gang Pan added: “We have shown in our experiments that simply by circulating polluted air through a small freezing chamber we can remove most of fine particles and gas pollutants.

    “Our study makes it possible to add an ‘air cleaner’ option to household appliances in areas which might experience extremely poor air conditions. By controlling indoor air pollution and improving air quality in this way, this work could be greatly beneficial for public health.”

    The study is reported in the journal Science of the Total Environment.

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      Nottingham Trent University (NTU) was named University of the Year 2017 at the Times Higher Education Awards, and Modern University of the Year in the Times and Sunday Times Good University Guide 2018. These awards recognise NTU for its high levels of student satisfaction, its quality of teaching, its engagement with employers, and its overall student experience. NTU has been rated Gold in the Government’s Teaching Excellence Framework – the highest ranking available.

      NTU is one of the largest UK universities. With 30,000 students and more than 4,000 staff located across four campuses, the University contributes £900m to the UK economy every year. It is one of the UK’s most environmentally friendly universities, containing some of the sector’s most inspiring and efficient award-winning buildings. 96% of its graduates go on to employment or further education within six months of leaving.

      NTU achieved an 88% satisfaction score in the 2018 National Student Satisfaction Survey.

      The University is passionate about creating opportunities and its extensive outreach programme is designed to enable Nottingham Trent to be a vehicle for social mobility. NTU is among the UK’s top five recruiters of students from disadvantaged backgrounds.

      NTU is home to world-class research, and won The Queen’s Anniversary Prize in 2015 – the highest national honour for a UK university. It recognised the University’s pioneering projects to improve weapons and explosives detection in luggage; enable safer production of powdered infant formula; and combat food fraud.

      With an international student population of over 3,000 from around 100 countries, the University prides itself on its global outlook

    Published on 8 November 2018
    • Subject area: Geography, horticulture and environment
    • Category: Press office; Research; School of Animal, Rural and Environmental Sciences