Particle filtration with HEPA is predicted to save the lives of 0.25 to 2.4 persons per 10,000 persons per population. An academic paper from 2017 states that: "The largest reductions in mortality were from interventions with continuously operating portable air cleaners in homes because, given our scenarios, these portable air cleaners with HEPA filters most reduced particle exposures" (Fisk & Chan, 2017).
Minimizing exposure to allergens and remediating the environment play a critical role in the treatment of asthma and allergies. The most effective environmental control measures include the use of HEPA filters (Wright and Phipatanakul, 2014).
A recent report by Zhao et al. (2015) showed that there were significant health and economic impacts when fine particulate matter (PM2.5) of outdoor origin is reduced inside residences. Annual monetary cost saving were between $1 and $1348 per person in the homes with HEPA filtration.
Enhancing the capacity of buildings to protect occupants from necessary exposure to outdoor particulate matter (PM) has major potential to improve public health outcomes. This is because PM exposure is linked with negative health including stroke, respiratory infections, heart attacks and other cardiopulmonary disorders and lung cancer (Bin Zhao, 2015).
A randomized controlled trial, evaluated the effectiveness of free-standing HEPA air filters (Batterman et al., 2012) in households of children with asthma. High concentrations of particulate matter (PM) and carbon dioxide were frequently seen. When indoor air quality was monitored, the HEPA filters reduced PM levels in the child's bedroom by an average of 50%. In conclusion, free-standing air filters can be an effective intervention that provides substantial reductions in PM concentrations if the filters are used.
It is known that asthma can be made worse by environmental factors including airborne particulate matter (PM). When homes with asthmatic children were supplied with free standing HEPA air filters for one week there was a reduction in overall PM in one-week by 68-80% (Due et al., 2011).

OTHER ACADEMIC LITERATURE:

Fisk, W.J. and Chan, W.R. (2017). Effectiveness and cost of reducing particle-related mortality with particle filtration. Indoor Air. Feb 7. epub ahead of print.
Holý, O., Matoušková, I., Kubátová, A., Hamal, P., Svobodová, L., Jurásková E. and Raida, L. (2015). Monitoring of microscopic filamentous fungi in indoor air of transplant unit. Central European Journal of Public Health. 23(4): 331-334.
Zhao, D., Azimi, P. and Stephens, B. (2015). Evaluating the long-term health and economic impacts of central residential air filtration for reducing premature mortality associated with indoor fine particulate matter (PM2.5) of outdoor origin. Int J Environ Res Public Health. 21(7): 8448-8479.
Bin Zhao, W.J. (2015). Estimating mortality derived from indoor exposure to particles of outdoor origin. PLoS ONE. 10(4): e0124238.,
Wright, L.S. & Phipatanakul, W. (2014). Environmental remediation in the treatment of allergy and asthma: latest updates. Curr Allergy Asthma Rep. 14(3): 419.
Batterman, S., Du, L., Parker, E., Robins, T., Lewis, T., Mukherjee, B., Ramirez, E., Rowe, Z. and Brakefield-Caldwell, W. (2013). Use of free-standing filters in an asthma intervention study. Air Qual Atmos Health. 6(4): 759-767.
Youcef Khoudja, R., Xu, Y., Li, T. and Zhou, C. (2013). Better IVF outcomes following improvements in laboratory air quality. J. Assist Reprod Genet. 30: 69-76.
Batterman, S., Du, L., Mentz, G., Mukherjee, B., Parker, E., Godwin, C., Chin, J. Y., O'Toole, A., Robins, T., Rowe, Z. and Lewis, T. (2012). Particulate matter concentrations in resiences: an intervention study evaluating stand-alone filters and air conditioners. Indoor Air. 22(3): 235-252.
Du, L., Batterman, S., Parker, E., Godwin, C., Chin, J-Y., O'Toole, A., Robins, T., Brakefield-Caldwell, W. and Lewis, T. (2011). Particle concentrations and effectiveness of free-standing air filters in bedrooms of children with asthma in Detroit, Michigan. Build Environ. 46(11): 2301-2313.
Sublett, J.L. (2011). Effectiveness of air filters and air cleaners in allergic respiratory diseases: a review of the recent literature. Curr Allergy Asthma Rep. 11: 395-402.
Sublett, J.L., Seltzer, J., Burkhead, R., Brock Williams, P., Wedner, H.J., Phipatanakul, W. and the American Academy of Allergy, Asthma & Immunology Indoor Allergen Committee. (2010). Air filters and air cleaners: Rostrum by the American Academy of Allergy, Asthma & Immunology Indoor Allergen Committee. J Allergy Clin Immunol. 125(1): 32-38.
Salam, Z-H.A., Karlin, R.B., Ling, M.L. and Yang, K.S. (2010). The impact of portable high efficiency particulate air filters on the incidence of invasive aspergillosis in a large acute tertiary-care hospital. American Journal of Infection Control. 38(4): e1-e7.
Cheong, C.D., Neumeister-Kemp, H.G., Dingle, P.W. and Hardy, G. St. J. (2004). Intervention study of airborne fungal spora in homes with portable HEPA filtration units. J. Environ. Monit. 6: 866-873.