Appendix 26. Germicidal ultraviolet lamps

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    Update: October 2023


    26.1 Use 

    • Germicidal ultraviolet (GUV) lamps emit UV-C rays. They are installed in the upper part of a room to create a "germicidal zone" where bacilli are killed.
    • They are suspended from the ceiling or mounted on the wall in fixtures with baffles that prevent the radiation from going downwards and thus reaching the people in the lower part of the room.
    • For an effective system:
      • Installation and maintenance should be performed by qualified technicians.
      • Irradiance in the upper part of the room should be in the range of 30 to 50 µW/cm2.
      • GUV lamps should irradiate the largest possible volume of the upper part of the room.
      • Effective air mixing is needed to direct the air (and the bacilli) to the germicidal zone. Effective mixing may be provided by natural convection currents or fans. However, when airflow speed is too high, effectiveness can be reduced because the time for bacilli irradiation is shorter.
      • Relative humidity in the room should be below 60%.
      • Room temperature should be between 20 and 24 °C.
      • In rooms with hospitalized patients, the GUV lamps should be switched on 24 hours a day.

    26.2 Installation

    • The height of the room should be minimum 2.5 m and GUV fixtures should be installed at a minimum height of 2.1 m.
    • A 30W GUV lamp is usually sufficient for 18 m² of room surface. However, the positioning of the lamp influences the size of the germicidal zone (e.g. wall-mounted lamps have a smaller germicidal zone than ceiling-mounted ones).
    • Reflective surfaces (i.e. oil painted ceilings, etc.) in the germicidal zone should be avoided.

    26.3 Maintenance

    • A staff member should check every day that the GUV lamps are on and work properly. Keep records of daily inspections.
    • Lamps and fixtures should be cleaned at least once a month (more often if necessary). The lamps must be turned off and cool then, wiped with a cloth dampened with 70% alcohol. Do not use water and soap or any type of detergent. Keep records of cleaning.
    • GUV level should be measured every 6 months and at least once a year using a GUV light radiometer. Irradiance measurements should be performed:
      • at eye level in different places in the lower occupied area of the room;
      • at 1 m from the fixture centre in all possible directions in upper irradiated area of the room.
    • National Institute for Occupational Safety and Health (NIOSH) recommends [1] Citation 1. National Institute for Occupational Safety and Health. Environmental control for tuberculosis: basic upper-room ultraviolet germicidal irradiation guidelines for healthcare settings. Publication No. 2009–105
      • a maximum of 0.4 µW/cm2 at eye level in lower occupied area, and
      • an average of 30 to 50 µW/cm2 in upper irradiated area (for UV-C with a wavelength of 254 nm).
    • Staff performing measurements should wear personal protective equipment (UV-protective glasses, thick clothing, and textile gloves) and use sunscreen with solar-protection factor > 15.
    • The lifespan of an UV lamp bulb is determined by the manufacturer (typically, 9000 hours of continued use). After this period, UV lamp bulbs rapidly lose effectiveness and must be changed. If a bulb has a 30% decline, it should be replaced before the scheduled time.

    26.4 Disposal

    • GUV lamps contain mercury and quartz and are hazardous waste.
    • The disposal process should be discussed before considering the use of GUV lamps.
    • Adequate disposal of GUV lamps is performed by specialist companies, not available in all countries. Seek advice from TB-IPC specialists for a context-dependent solution.

    26.5 Safety considerations

    • GUV exposure may be harmful. Skin exposure may cause erythema and eye exposure may cause conjunctivitis (feeling of sand in the eyes, tearing) and/or keratitis (intense pain, photophobia). Symptoms appear 6 to 12 hours after exposure.
    • Even if these adverse effects are reversible, staff should report them immediately to the TB-IPC practitioner. It could mean that GUV irradiation is higher than acceptable levels in the lower area of the room.
    • Staff training should include basic information on GUV lamps, their potential harmful effects if overexposure occurs, and the personal protective equipment to be used when handling the lamps.