Article Review: Natural Ventilation for the Prevention of Airborne Contagion
Intro:
Tuberculosis is a major risk to health and can be easily spread through tiny liquid drops expelled from coughing, sneezing, spitting or talking. Risk of transmission in hospitals is higher due to close contact with others. It is recommended that air be changed with fresh air 6-12 times per hour. Air changes can be achieved through opening windows and doors, using mechanical ventilation that keeps the air pressure in an isolation ward lower than outside it, also called negative pressure. Where negative air pressure isolation rooms are difficult to implement, natural ventilation offers a low-cost alternative.
Methods and findings:
- Study done in 8 hospitals in Lima, Peru
- 5 hospitals built prior to 1950, 3 hospitals built between 1970-1990
- Focused on 70 naturally ventilated rooms that housed infectious patients
- Compared against 12 mechanically ventilated negative air pressure isolation rooms built post 2000
- Infection risk estimated for TB exposure using the Wells-Riley model of airborne infection
Conclusions:
- Opening windows and doors allows for maximum natural ventilation which results in the risk of airborne contagion being much lower that is would be with high-maintenance and costly mechanical ventilation systems
- Natural ventilation ideal for limited-resource areas and tropical climates where risk of TB is greatest
- Windows and doors should be opened where respiratory isolation is difficult
- High ceilings and large windows also provide better airflow and thus reduce risk of infection
Source: Escombe AR, Oeser CC, Gilman RH, Navincopa M, Ticona E, Pan W, et al. (2007). Natural Ventilation for the Prevention of Airborne Contagion. PLoS Med 4(2): e68. https://doi.org/10.1371/journal.pmed.0040068