Recommendation 2

For natural ventilation, the following minimum hourly averaged ventilation rates should be provided:

  • 160 l/s/patient (hourly average ventilation rate) for airborne precaution rooms (with a minimum of 80 l/s/patient) (note that this only applies to new health-care facilities and major renovations);
  • 60 l/s/patient for general wards and outpatient departments; and
  • 2.5 l/s/m3 for corridors and other transient spaces without a fixed number of patients; however, when patient care is undertaken in corridors during emergency or other situations, the same ventilation rate requirements for airborne precaution rooms or general wards will apply.

The design must take into account fluctuations in ventilation rate.

When natural ventilation alone cannot satisfy the recommended ventilation requirements, alternative ventilation systems such as a hybrid (mixed-mode) natural ventilation system should be used, and then if that is not enough, mechanical ventilation should be used.

Population: Health-care settings

Intervention: Natural ventilation

FactorDecisionExplanation
Quality of evidenceLowThere is no direct evidence available to suggest the direct impact of natural ventilation on disease transmission, though there is strong engineering evidence that natural ventilation can achieve a very high ventilation rate and it is suggested that a high ventilation rate can reduce airborne infection (Menzies et al., 2000).
Benefits or desired effectsModerate (benefits sometimes outweigh disadvantages)Suitable for mild or moderate climates.
Lower capital, operational and maintenance costs.
Capable of achieving very high ventilation rate.
Large range of control of environment by occupants.
Disadvantages or undesired effectsEasily affected by outdoor climate.
More difficult to predict, analyse and design to ensure airflow direction control.
Reduces comfort level of occupants when hot, humid or cold.
Inability to establish negative pressure in isolation areas, but may be provided by proper design; depends on situation.
CostsMay be low and highLow cost if simple ventilation is used and properly designed with suitable climate.
Can be higher if hybrid (mixed-mode) ventilation or high-tech natural ventilation is used.
FeasibilityConditional to country settingsNatural ventilation is less feasible in extreme climates (extreme cold, hot, noisy, polluted).
Overall rankingCONDITIONAL RECOMMENDATION
Research gapThere is a need to determine the natural ventilation requirements in terms of variable ventilation rate and variable airflow direction for infection control in health-care settings.

From: Annex B, Recommendation GRADE appraisal tables (GRADE system)

Cover of Natural Ventilation for Infection Control in Health-Care Settings
Natural Ventilation for Infection Control in Health-Care Settings.
Atkinson J, Chartier Y, Pessoa-Silva CL, et al., editors.
Copyright © 2009, World Health Organization.

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