Verification of Bacteria Inactivation Efficiency of Steril-Aire UVC Emitters at TTSH AHUs

Testing carried out at: AHU 1-1 & AHU 1-2 (Tan Tock Seng Hospital Medical Centre)

UVC emitters deployed: Steril-Aire DE Series UVC emitters

Date of test: 3 Sep 2015

Test conducted by: IAQ Consultants

Proposed Methodology

Two AHUs chosen for the tests have the following UVC emitter configurations:

AHU 1-1: 4 rows of UVC emitters with spacing of 14.5 inches (368 mm) between UVC emitters.

AHU 1-2: 4 rows of UVC emitters with spacing of 11.5 inches (292 mm) between UVC emitters.

At each AHU two bacteria air sampling test will be carried out simultaneously using Merck MAS100

Air Sampler. The sampling duration for the airborne bacteria test is 1 minute during which the

sampler collects 100 litres of air.

Two IAQ specialists will be involved with the simultaneous air measurement at:

Just before the air filters Just after the UVC emitters

Three periods of air sampling are proposed:

Morning at around 9.30 am Lunch time at around 12.30 pm Afternoon at around 3.30 pm

Steps to Be Taken for Each Bacteria Sampling Test with UVC Lamps Switched Off

1. Switch off AHU fan.

Sampling of bacteria

before air filters

Sampling of bacteria

after UVC emitters

2. First IAQ specialist with Merck MAS100 Air Sampler to be stationed at mixed air section of AHU.

3. Switch off UVC emitters. 4. Second IAQ specialist with protective face mask enters AHU via AHU door with Merck

MAS100 Air Sampler. 5. Close AHU door and start AHU fan. 6. Give signal (by knocking on AHU) to both IAQ specialists to start air sampling. 7. Give signal (by knocking on AHU) to both IAQ specialists to stop air sampling after one

minute. 8. Stop AHU fan and allow second IAQ specialist to get out of AHU. 9. Start AHU fan.

Steps to Be Taken for Each Bacteria Sampling Test with UVC Lamps Switched On

1. Start this test 15 minutes after the last test (with UVC lamps switched off). 2. Switch off AHU fan. 3. First IAQ specialist with Merck MAS100 Air Sampler to be stationed at mixed air section of

AHU. 4. Second IAQ specialist with protective face mask enters AHU via AHU door with Merck

MAS100 Air Sampler. 5. Close AHU door and start AHU fan. 6. Give signal (by knocking on AHU) to both IAQ specialists to start air sampling. 7. Give signal (by knocking on AHU) to both IAQ specialists to stop air sampling after one

minute. 8. Stop AHU fan and allow second IAQ specialist to get out of AHU.

9. Start AHU fan.

Photos Taken

Team Preparing for the Test Team Preparing for the Test

Internal View of AHU 1-2 IAQ Specialist inside AHU 1-2 Collecting

Bacteria on Air Sampler after UVC Emitters IAQ Specialist Fully Attired

Air Sampler Collecting Bacteria

Just Before the Air Filters

IAQ Specialist inside AHU 1-1 Collecting

Bacteria on Air Sampler after UVC Emitters