Vol.17 No.4 THE HONG KONG UNIVERSITY OF SCIENCE AND TECHNOLOGY December 2008
HEALTH, SAFETY AND ENVIRONMENT OFFICE
The current issue of Safetywise has been published in electronic format and it can be accessed at :
http://www.ab.ust.hk/hseo/sftywise.htm
December 2008 PDF Version
Office Ventilation and the Recent Installation of the Thermostat Control Switch Sustainability Effort Continues to Take Shape at HKUST
Realizing a Better Way to Disinfect at HKUST Green Laser Pointer – Be on Guard
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Office Ventilation and the Recent Installation of the Thermostat Control Switch
The ventilation system serving the office block consists of two main components, namely the Air Handling Unit (AHU) on the rooftop and the Fan Coil Unit (FCU) on each floor. The AHU is responsible for supplying fresh air to the FCUs on each floor of the office block. The AHU normally runs before the regular office hours begin and stops late at night. Due to the positive duct pressure exerted by the fresh air unit, the fresh air supply to a FCU is continuous regardless of the operating status of the FCU. The amount of fresh air delivered to FCUs is determined according to relevant applicable indoor air quality standards. These standards are established to ensure adequate fresh air is supplied to indoor environment to maintain optimal occupants’ comfort.
The FCU is responsible for further conditioning of the treated air supplied to the room by the AHU. Each FCU is equipped with a thermostat and control switch on the wall which controls the on/off of the connected FCU. The FCUs are connected together to a large group with its operation time centrally controlled by the building automation system. When running, each FCU mixes the room returned air at the return air plenum with additional fresh air from the AHU. The mixed air will be re-distributed to the room by the FCU. Part of the mixture is continuously extracted out from the room to allow for continuous supply of fresh air. The FCUs have limited effect on the amount of fresh air delivered to each office as this task is primarily handled by the AHU. A typical ventilation system is shown in Fig. 1
Recently FMO had replaced all of the air-conditioning control switches in offices with a more advanced type of control that allows better and more flexible temperature control in offices. Questions had been raised by occupants concerning whether such a replacement will have any impact on the indoor radon level and the amount of fresh air delivered to offices as the new control switch shuts off the FCU automatically at a predetermined schedule. As described above, the control switch controls only the operation of the FCU, which in turn, conditions the treated air from the AHU. It does not have any control over the amount of fresh air delivered to each room or only has minimal effects at best. HSEO has monitored radon levels in offices where the new control switches had been installed (Fig. 2). Apparently, the radon concentration variations follow closely with the operating time of the centralized AHU regardless of the operating status of the FCU. Moreover, HSEO will continue to carry out the ongoing monitoring of the radon levels in office area to ensure the performance target (of an average of 150 Bq/M3 or below between 8AM to 10PM, Monday to Friday) will continue to be met.
(Information in this article was provided jointly by FMO and HSEO)
Figure 2. Radon concentration variation recorded in an office equipped with the new control switch. Radon concentration varies with the operating time of the AHU but not the FCU.
Following last June’s environment week which highlighted the need to promote and realize sustainability on our campus, much effort has been dedicated to moving forward on this mission.
UAC has authorized the formation of an Environmental Sustainability Steering Committee to help coordinate effort among students, faculty, staff and alumni at HKUST to increase awareness and understanding of environmental issues, to facilitate our contribution to addressing environmental sustainability issues through teaching and research, and to help formulate actions to reduce HKUST’s impact on the environment. The Committee has now met to map out strategies and to set goals towards achieving this mission.
A sustainability project coordinator has been appointed to work with students to learn and practise environmental sustainability. Upon his arrival in January 2009, he will also work with faculty members to incorporate sustainability lesson plans into various academic disciplines.
In the meantime, this year’s sustainability launch drew interested staff and students together to brainstorm on the way forward. In addition, this year’s sustainability student project competition has been announced. Sponsorship from Hang Seng Bank has been secured again to reward students who will come up with innovative and achievable ideas about environmental sustainability.
Students participating in the Organic Farming Club are working with officers of the Students Union to explore the idea of forming a sustainability society to help promote proper culture and practices among students in a sustainable manner. A group of MBA students are also exploring the feasibility of establishing a local chapter of Net Impact to help identify and promote issues and projects that can contribute to making a difference.
SAO has launched a Green Ambassador program to identify students who are willing to help promote environmental sustainability on our campus in the Hong Kong community. The program will initially provide training on a wide scope of environmental sustainability issues. It is anticipated that once the “basic training” is completed, these Green Ambassadors will reach out into the campus community to help fellow students to adopt a sustainable lifestyle. They will also reach out into the general community to work with
Sustainability Effort
Continues to Take
Shape at HKUST
primary and secondary school children to promote knowledge and popularize practices related to sustainability.
CELT had launched a session to help faculty members to teach sustainability concepts. It has been recognized that regardless of the academic discipline, the concept can be integrated to help students comprehend the far reaching impact of sustainability concerns.
A meeting in early 2009 has been scheduled for local universities to share experience on sustainability practices in academic institutions. This will be a useful forum to facilitate experience sharing and collaboration among institutions.
It is evident that much effort has been dedicated to formulating ideas and compiling action plans to raise awareness among members of our campus community on environmental sustainability. Let’s work together to help make a difference. If you have ideas you would like to share, please contact Dr David Mole (e-mail : [email protected]), secretary of the Environmental Sustainability Steering Committee. Alternatively, Professor Alexis Lau (e-mail : [email protected]) and Dr Joseph Kwan (e-mail : [email protected]), co-chairs of Environmental Sustainability Steering Committee, would also like to learn about your suggestions.
Realizing a Better Way to Disinfect at HKUST
We have discussed the need to change our reliance on formaldehyde for gaseous disinfection to a less toxic disinfectant in an earlier Safetywise article in May 2008
http://www.ab.ust.hk/hseo/sftywise/200805/page3.htm. Subsequently, Health, Safety and Environment Office (HSEO) was able to secure resources to purchase a hydrogen peroxide generator which can meet our needs in this regard.
The generator was manufactured by Bioquell, with a model name of Clarus L. It is capable of disinfecting up to 10m3 of space. In late November 2008, Bioquell personnel came to HKUST for testing and commissioning of the unit. They conducted a demonstration of biological safety cabinet (BSC) disinfection, using a Nuaire 425, which is the commonest BSC model on our campus.
The three-day T&C went smoothly. The effectiveness of the disinfection process was proved by exposing small metal discs each containing more than one million spores of
Geobacillus stearothermophilus to the hydrogen peroxide vapor. This particular strain of bacteria was known to be resistant to high temperature as well as hydrogen peroxide. Within
the designed contact time of a couple hours, all the spores located inside the BSC were wiped out by the disinfectant, which was demonstrated by the lack of growth after the discs were dropped into bottles containing culture medium afterwards.
The hydrogen peroxide disinfection cycle took a shorter time than formaldehyde fumigation, which typically required 6 hours of contact time. The hydrogen peroxide generator circulates the vapor throughout the process, and it maintains a negative pressure inside the BSC, therefore even if sealing of the unit is not perfect, the vapor will not leak out into the
room. This containment of the hydrogen peroxide vapor was demonstrated by non-detectable reading by a handheld hydrogen peroxide detector during the trial run. The negative pressure operation condition further improved safety of the disinfection cycle.
Subsequently in early December, 2008, the Clarus L hydrogen peroxide generator was coupled with a newly acquired animal cage washer at the Animal and Plant Care Facility (APCF), and a disinfection cycle was successfully demonstrated by the cage washer supplier personnel. This combination not only allows animal cages to be disinfected when necessary, it can also convert the cage washer into a disinfection chamber, and allows large pieces of equipment to be disinfected by hydrogen peroxide vapor when necessary.
In the coming months, HSEO and FMO Laboratory Services colleagues will conduct further BSC disinfection testing by ourselves, so that we can be more familiar with the operation of the equipment, and also to demonstrate disinfection effectiveness in other models of BSC. We will also closely collaborate with APCF colleagues to optimize the use of the hydrogen peroxide generator on campus. We have no doubt this hydrogen peroxide generator represents a major step forward for our biological safety program, by realizing a better way to disinfect at HKUST.
Green Laser Pointer – Be on Guard
The advances in laser technology application over the past few decades had made people wonder what life would be like if we had not discovered the beauty of the process. “Light Amplification by Stimulated Emission of Radiation” is a process which is now known as Laser. We can find laser in multitude of consumer products such as printer, scanner, video CD, medical equipment, laser pointer, etc. Laser has not surprisingly become our faithful servant just like pen and pencil. The use of laser pointer for teaching and presentation is very much a routine. However, how many users are aware of the potential problems associated with its use?
Just pressing one button, a presenter can clearly pinpoint to the audience the message on the presentation slide which is many meters away. The highly focused light beam generated by the laser pointer can travel a long distance without diverging and create a bright spot on the surface it illuminates. Since the beam does not diverge, it conserves very much all of its energy after leaving the barrel and before hitting the target. It is exactly this advantage which makes laser pointer so popular but at the same time presents a safety concern. When the highly focused laser beam comes into contact with biological tissues, the intense laser beam, depending on where it lands, could cause serious burn to the tissues. In particular, human eyes and skin are most susceptible to laser injuries. Eye and skin exposures to laser beam must be avoided.
Conventional laser pointer usually comes with a low-powered red laser. The laser beam of the pointer is generated by a laser diode which produces the red wavelength. Since the power of the laser beam is relatively low, proper use of the pointer will not normally cause any safety concerns. Recently, a more attractive green laser pointer is available in the market. The green laser pointer has a definite advantage over the red as human eyes’ response to the green wavelength is far more sensitive than the red. The green dot appears much brighter to the audience than the red dot. However, the laser diode which produces the green wavelength is not commonly available and it takes a complicated set-up to generate the green beam. With the set-set-up, the power of the green laser pointer can easily go over 100mW, whereas, the power of the conventional red pointer is normally less than 5 mW. There is no shortage of video clippings in the internet showing what a powerful green laser pointer can do and it needs no further illustration about the damages a green laser point can inflict to our eyes and skin. With the growing popularity of using green laser pointer in the classroom settings, users should pay more attention to the hazards associated with the use of green laser pointer. To ensure safe use of the green laser pointer, user should not use any green laser pointer which has a power greater
than 5 mW and as a habit, never point the beam at anyone. Certainly, the use of high-powered green laser under research settings is common but use it in the classroom setting is far too risky. The use of high-powered green laser pointer for presentation and classroom teaching should be strictly prohibited.
