Ref. : GRG/1/50A/3 Pt. 1Electrical & Mechanical Services Department98 Caroline Hill Road,Causeway Bay,Hong Kong.

10 July 2000

EMSD Technical Circular No. 3/2000

Guidelines for Prevention of Legionnaires’ Disease

Purpose

In line with the recent publication of the revised Code of Practice for the Prevention ofLegionnaires’ disease, this circular serves to:-

(a) Ensure that all officers concerned are aware of the role of EMSD and the latestdevelopment in the prevention of Legionnaires’ disease.

(b) Adopt appropriate measures in handling the relevant design, operation andmaintenance of engineering plants/equipment.

EMSD Technical Circular No. 1/90 is hereby superseded.

Background

2. The bacteria causing Legionnaires’ disease, like other kinds of bacteria, are widespread in natural water sources and have been found in rivers, lakes, streams, mud and soil, aswell as man-made water systems. Infection of the disease is caused by inhaling airbornedroplets (i.e. aerosols) or particles in fine mist containing the bacteria into the lungs wherethey are deposited. The operation temperature of evaporative cooling tower is optimal to thegrowth of the bacteria while the spray cooling process in such cooling tower will easily leadto the dispersion of aerosols to the surroundings. Therefore, improperly designed and/oroperated and maintained cooling towers have been one of the main causative agents ofLegionnaires’ disease.

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3. Following the outbreak of Legionnaires’ disease in the UK during 1985, thePrevention of Legionnaires’ Disease Committee (PLDC) was set up in Hong Kong. TheCommittee is chaired by EMSD and comprises representatives from various governmentdepartments/bureau and two local universities.

Current Development

4. Since March 1994, Legionnaires’ disease has been listed as a notifiable disease underthe Quarantine and Prevention of Disease Ordinance (Cap. 141). According to theDepartment of Health, there were 10 reported cases of Legionnaires’ disease in Hong Kongbetween 1994 and 1999, all of which were sporadic cases with no evidence of clustering.

5. Furthermore, the disease has been classified as a notifiable occupational disease sinceJune 1999 under the Occupational Safety & Health Ordinance (Cap. 509) and the Employees’Compensation Ordinance (Cap. 282).

Code of Practice

6. In 1994, the PLDC published a Code of Practice for the Prevention of Legionnaires’Disease (COP) to provide guidelines for the design, installation, operation and maintenanceof air-conditioning and water systems, especially cooling towers and centralized hot watersystems, for the effective control and prevention of the Legionnaires’ disease.

7. The revised COP was published in early 2000 and has been distributed to variousprofessional bodies, contractors associations, hospitals, etc. This COP can also bedownloaded from the EMSD homepage at http://www.info.gov.hk/emsd.

Guidelines

8. All officers concerned are requested to observe the following:-

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(a) New projects

(i) The design precautions as stated in the COP shall be incorporated wheneverpracticable.

(ii) For projects where the necessary modifications cannot be included at this stage,provision shall be allowed for possible future improvements.

(b) Existing Installations

(i) The existing systems shall be modified as necessary to incorporate theoperation and maintenance precautions as stated in the COP.

(ii) In case alterations to existing systems are not practical at this stage, thenecessary modification work shall be included in future overhaul and/orreplacement programme as far as possible.

(LEUNG Cham-tim)Director of Electrical and Mechanical Services

Distribution

All Assistant Engineers & AboveAll Section Heads

c.c. S for WSPLSEFAD/BS, Arch SDAD/E&M, DSD