Ergonomic Analysis of Computer Laboratory - Assignment Example

Ergonomic Analysis of Computer Laboratory April 29, Table of Contents I. Introduction Albert Einstein n.d citedin Glavanis 2008) once said, "I never teach my pupils; I only attempt to provide the conditions in which they can learn." And after all these years, conditions for learning have yet to be perfected by learning institutions as they continue to build learning areas that have poor ergonomics. Such is the topic of this paper; it is the analysis of a computer laboratory that may need areas for improvement in ergonomics and anthropometry, as it presently lacks the optimum conditions for maximum learning. II. Ergonomics Ergonomics is the "science of work: of the people who do it and the ways it is done; the tools and equipment they use, the places they work in, and the psychosocial aspects of the working situation (Pheasant 1996, p.4)." The words was first coined by Professor Hywell Murell as part of forming a society of professionals seeking to research on the efficiencies of men-at-war and apply such learning for war recovery. Ergonomics comprise of two Greek words ergo meaning work and nomos meaning natural law (Pheasant 1996, p.5). Putting the two words together and in the context of Pheasant's definition, one may think that Ergonomics focuses on activities involving work, however as the discipline has evolved, it took on a greater extent. In applying ergonomics, one need not place a person during work hours to determine a need for correct fit of his surroundings. A person maybe on a daily routine preparing for work or going to the grocers after work, and yet those activities require the same scientific study of correct design and movement in order to ensure that the individual will be injury-free. Thus, a modern definition of ergonomics would encompass activities related to work as well as those that are "not directly connected to making a living" (Adler ed. 1999, p. 2-4). The significance of ergonomics is its contribution to the individual as well as the environment where such individual exists. According to the Health and Safety Executive Labor Force Survey of 2008/09 (2010, p. 11) , about 227,000 workers reported work-related injuries of the back which is caused or made worse by their current job and about 84,000 complained of injuries in their upper limb and neck. Both injuries combined caused about an average of 32 days per year lost work day for each of those complainants. If there was proper ergonomic considerations in the places of work that such complainants have, those injuries would have been avoided. Columbia Encyclopedia thus defines ergonomics as "the engineering science concerned with the physical and psychological relationship between machines and the people who use them. The ergonomicist takes an empirical approach to the study of human-machine interactions. The objective is to improve the efficiency of operation by taking into account a typical person's size, strength, speed, visual acuity, and physiological stresses, such as fatigue, speed of decision making, and demands on memory and perception. Applications range from the design of work areas (including office furniture, automobile interiors, and aircraft cockpits) to the disposition of switches and gauges on the control panels of machinery to determining the size, shape, and layout of keys on computer terminals and character height, color, and clarity on video displays" (Lagass ed. 2009). III. Anthropometrics The main component in ergonomic design is the dimensions of the human body being considered. Anthropometrics therefore is the science that deals with these specific human measurements and plays a big role in ergonomic design. In considering human measurements, the average dimensions maybe taken into consideration, but will not satisfy the majority. The better approach is to take a range that will satisfy a significant portion of the population, with the use of distribution curves. On a normal distribution curve, one will get the 5th, 50th and 95th percentile of the distribution as significant points of reference to consider dimensions. Below are some parameters for dimensions of British adults (Adler ed. 1999, p. 2-3): Men Percentiles Women Percentiles 5th 50th 95th 5th 50th 95th Standing 1. Stature 1625 1740 1855 1505 1610 1710 2. Eye Height 1515 1630 1745 1405 1505 1610 3. Elbow Height 1005 1090 1180 930 1005 1085 Sitting 1. Height above seat level 850 910 965 795 850 910 2. Shoulder height above seat level 540 595 645 505 555 610 3. Eye height above seat level 735 790 845 685 740 795 4. Elbow above seat level 195 245 295 185 235 280 5. Popliteal height 395 440 490 355 400 445 6. Buttocks, popliteal height 440 495 550 435 480 530 7. Rear of buttocks to front of knees 253 325 395 245 315 385 8. Extended leg length 985 1070 1160 875 965 1055 9. Seat width 310 360 405 310 370 435 In considering the design of seat height for example, we can consider the popliteal height of the buttocks and design a seat that is at least 435mm and can be adjusted to as much as 550mm since such a range covers that significant population of British males and females. IV. Applicable Standards A. Thermal Thermal comfort is an overwhelming yet achievable objective. The key is to balance the various factors affecting thermal comfort, i.e., the room temperature, movement of air, relative humidity as well as the activity of the people using the room. Each of these factors will be discussed following. The human body generates heat from its basic processes, blood circulation, digestion, musco-skeletal activities to name a few. In room design, the objective is to keep the body temperature at 37 C. Below are various activities and their corresponding metabolic heat (MET) generated expressed in Watts (W) (Adler ed. 1999, p. 38-5): Activity MET Sensible (W) Latent (W) Seated at rest (theatre, hotel lounge) 1.1 90 25 Light work (office, dwelling, school) 1.3 100 40 Standing activity (shopping, laboratory) 1.5 110 50 Standing activity (shop asst., domestic) 2.2 130 105 Medium activity (factory, garage work) 2.5 140 125 Heavy work (factory) 4.2 190 250 Clothing can also influence thermal design. Clothing, measured in CLO, controls the loss of body heat of people and must be considered when designing a space. Values to be considered are as follows (Adler ed. 1999, p. 38-7): CLO m2K/W Nude 0 0 Light summer clothes 0.5 0.08 Light working ensemble 0.7 0.11 Winter indoor 1.0 0.16 Heavy business suit 1.5 0.23 The temperature of the air is a significant parameter in achieving thermal comfort. The Chartered Institution of Building Services Engineers (CIBSE) recommends a range of 19 - 23 C air temperature during winter season and less than 27 C during summer (Adler ed. 1999, p. 38-6). Radiant temperature is composed of all things in a room that can give off heat. In the computer room for example, the energy from the sun coming into the windows, plus the energy from the computers, lights, and the people inside the room will contribute to the radiant temperature. Air speed also affects air temperature. The perception of air movement, which is felt at 0.2 m/s, could cause discomfort for people. If draught is unavoidable, the chart below shows that increasing air temperature can counter the discomfort. Relative humidity (RH) measures the amount of vapor in the air present compared to the total amount of vapor it can hold, given a certain temperature. Two tools are used to measure RH, a wet bulb thermometer, which basically evaporates to reflect the temperature and a dry bulb thermometer which detect the heat from the surrounding air. When combining the two temperatures, a psychometric chart will show the corresponding RH. CIBSE recommends that RH be between 40 - 70% to maintain thermal comfort (Adler ed. 1999, p. 38-7). In recent developments, a simplified method of designing thermal comfort was established and described in detail under EN ISO 7730. Combining relative humidity, air temperature, air speed and radiant temperature as well as metabolic activity of people and average clothing parameters, Fanger came up with a calculation of comfort combining all the parameters (Saberi et al. n.d., p.4). Such comfort equation became the basis of a set of seven thermal sensations: hot, warm, slightly warm, neutral, slightly cool, cool and cold. A large group of people were subjected to such sensations and their responses were charted and called the predicted mean vote (PMV). In addition, the percentage of people dissatisfied (PPD) is the distribution of population that will be dissatisfied at the sensations. This PMV-PPD relationship is now used as a typical means of designing thermal comfort as defined by the European Committee of Standardization (2007, p.41) in EN ISO 7730. B. Lighting Adequate lighting is a must in learning. One needs to see clearly the subject at hand in order to absorb whatever learning is available. Appropriate lighting therefore is required in the design of learning areas. There are several factors that affect the appropriateness of lighting. Firstly, the amount of light flowing from a light source, called lumen (lm) - 1360 lm is emitted from a 100-watt incandescent lamp (Tregenza and Loe 1998, p. 3). When measuring the intensity of light in a given the angle of the light beam or a steradian, it is measured in candelas (cd) - 1 candela is 1 lumen per steradian. Both measures are used by designers to define requirements and capability of lighting fixtures. From a user's stand point, Illuminance expressed in lux(lx), or the amount of light falling on a surface as well as the objective brightness or luminance expressed in candelas per square meter would be the practical measures in assessing requirements for lighting. According to EN-12464-1 (ECS 2007, p. 41), educational buildings, particularly classrooms for adult education should have a maintained illuminance of 500 lx and a lower level of 300 lx for general classroom design. There is consideration to be made if the primary purpose of the room involves the intense use of computers. Thus, a straightforward design based on a classroom set-up will not be applicable. The use of computer monitors or technically called visual display terminals (VDT) is affected by brightness of its surroundings because the panels are made out of glass and thus, reflects light. To avoid reflection, the lighting layout should ideally be in parallel with the VDT user configuration. This way, illumination flow is directed downward to the VDT surface and allows for better control of glare. If the lighting fixture is perpendicular to the VDT, the problem of glare and reflection will already be apparent. When VDT is used in a room with side windows, the light coming from the window will be reflected on the panel if the user is turned away from the window. If the user is facing the window while using a VDT, it may present a glaring brightness which will prevent the user from seeing the display. If adjacent to a window while using a VDT, Adler (1996) recommends that the display be at right angles. However, if both sides of the panel are adjacent to a window, it is best to block off the light and depend on electrical lighting instead. For ceiling heights greater than 2.5m, uplighters are recommended to provide for controlled ambient lighting while for ceiling heights less than 2.5m, the use of luminaires with restricted side lighting to control VDT glare and/or reflection is recommended. The Chartered Institution of Building Service Engineers (1993) categorized luminaires by its brightness limitation angle as follows: Category VDT Use Brightness illumination angle 1 Intense 55 2 General 65 3 Minimal 75 Such angle provides a brightness limit of 200 candelas per square meter. As for viewing distance, Pheasant (1996 p.94) recommends an ideal distance of 750mm between the user and the VDT with an absolute minimum of 500mm. Thus, a table width of about 1m will be ideal when using VDT. Lighting control is another aspect to consider. Automated controls which can be dictated by illuminance level, daylight level or time requirements are always ideal. It allows for greater flexibility in using the space as well as ensures efficient use of lights only when needed. C. Acoustic The focus of this section on acoustics is on noise. In an enclosed room, various factors can affect noise - mechanical cooling, sound from the outside as well as the activity inside the room. It will be ideal for a room to be enclosed all the time in order to control noise, however if not possible, the conservative approach of an open window set-up should be considered. The British Standard EN: 15251 specify that for a classroom set-up, the noise design level should be at 35dB and should range between 30 - 40 dB (cited in Adler ed. 1999, p. 40-2). Anything beyond the limits would impair the learning ability in the room. D. Office Design According to Pheasant (1996, p. 94), there are two guidelines that will be applicable for office furniture and workstations: BS 5940 (1980) which deals with furniture and BS 7179 (1990) which deals with visual display terminals which is now superseded by BS EN 29241 (1993) which is in turn based upon the International Standard ISO 9241 (1992). D.1. Desk BS 5940 the recommended height of worktops should be 720 +/- 10 mm. This is very much applicable for paper-based work. However, for computer-based work, the location of the keyboard must be lower than such height to avoid strain on the wrists especially during prolonged typing. About 30 - 50mm lower would be ideal. Based on the British Standard of Office Furniture, the ideal table height is 720 mm +/- 10 mm for work desks using paper-based work. Similarly, the same is the recommended height for placement of keyboard based on BSI 7179 (Pheasant 1996, p. 95). Ideally, desks for use with key boards should be at elbow level which is 50 mm below the top of the desk. In the current set-up the tables are even below this minimum and do have impact on the user. For a short person to work with this table, he or she has to compensate with using an adjustable height chair. The danger though is that adjusting to a high level chair may leave the user to lack proper footing, which can be solved with a footrest. Another tendency is to sit at the edge of the heightened chair to reach what is in the table, in this case not being able to use a back rest. To this point, one can use additional back pillow to compensate. On the other end tall users may find themselves slouching on the desk or having to adjust their chair to the lowest position and cramping their legs to enjoy a comfortable desk height. BS 5940 specifies a range of 670-770 mm and BS 7179 specifies 660-770 mm (Pheasant 1996, p. 97). The recommended solution is to replace the desks with adjustable height desks. D.2. The Chair By fundamental ergonomics and anthropometrics, the workstation chair should fit the varied dimensions of the possible users. Therefore, an ergonomic chair is one that is fully adjustable in the various aspects of seat height, back support, seat distance and arm rests. D.2.a) Seat height Basing on the representative dimensions of the British adult in p. 4, the seated elbow height ranges from 195 - 295 mm. Deducting the range from the 720 mm standard worktop height, an adjustment height of 425 - 535 mm would aptly consider the varying heights for the majority of British male and female. D.2.b) Back Support Basing on the representative dimensions of the British adult in p. 4, the varying should heights at seated level ranges from 505 - 645 mm or a delta of 140 mm between the 5th percentiles of women to the 95th percentile of men. Thus, an adjustment range similar to the delta would be a good ergonomic design. Recent studies also mandate that a full back support, covering the top of the shoulder over the entire back is a minimum requirement for ergonomic chairs. In addition, the backrest should also be adjustable to the angle of the seated position, thus the inclusion of a lockable tilt mechanism to the back rest is a must. A range of 5 forward to 5 backwards vs. the perpendicular position of the back should be made available (Pheasant 1996, p. 98). Lastly, the contour of the back rest should conform to the lumbar shape of the back D.2.c) Arm Rests Arm rests on chairs is already a must for all workstation chairs regardless of position (staff to executives). This provides the ability to support the arms of a computer keyboard user, even as the user is seated back on the chair. Referring to the dimension table in page 4, the range of elbow heights above the seat level is 455 - 595 mm or a range of 140 mm from the 5th percentile of British women to the 95th percentile of British men. Depending on the height of the arm rest attached, an adjustment of the said range must be made available to support ergonomic design. 3. VDE Regulations The Health and Safety Commission/Executive (2003, p. 5) mandated regulations on the safe use of VDTs in 1992, called the VDU Regulations or Display Screen Equipment Regulations of 1992 (and amended in 2002). This is also based on ISO 9241 but focuses more on the use of VDTs as compelled by the increasing upper limb injuries resulting from poor VDT ergonomics. In summary, the law requires employers to do the ff.: "Analyse workstations to assess and reduce risks; Ensure that workstations meet specified minimum requirements; Plan work activities so that they include breaks or changes of activity; Provide eye and eyesight tests on request, and special spectacles if needed; Provide information and training". While such regulations are intended for employers and for users in the workforce, the regulations should also be applicable to the room being analyzed in this paper. The Regulations provide for a checklist of various items to see if the current set-up is in compliance to the law. If there are non-compliant items, it is the employer's responsibility, in this case, the university's, to correct the deviation and follow the regulation for pain of consequence. The full checklist can be found as part of the guide provided in the HSE website at http://www.hse.gov.uk/pubns/priced/hsg90.pdf. Found on pages 15 - 21. Significant parts of the checklist on display set-up, keyboard and workstation set-up are shown on the succeeding pages. V. Current Measurements and Comparison to Standards A. Thermal Upon gathering the temperature in the room, the dry bulb/ wet bulb thermometer method was used and indicated in the lay out above. The location is close to the sea, and thus the relative humidity is more of a concern than the air temperature alone. Based on the measurements, an average reading of 22.5 C dry bulb and an average of 12.5 C wet bulb temperature were obtained. The dry bulb temperature readings ranged from 21 - 25 C while the wet bulb temperatures were stable at bet 12.5 - 13 C. Plotting the readings on the psychometric chart below, the resulting RH of the averaged temperature readings would be at 36% RH, while the room ranges in RH readings from 28% to 40% RH given the range of dry bulb temperatures. Near the windows, the RH is higher than inside the room, towards the walls. Such readings are below the thermal comfort standard of 40 - 70% RH. A low RH means that the air inside the room is dry, i.e., it can take in more water vapors in the atmosphere than what it already has. This may be affected by the fact that the room is close to the sea and the outside air is absorbing most of the vapors in the room to saturate the outside air. When the RH is below thermal comfort conditions, the skin tends to dry out resulting to chapped skin that turns to itch. This can be uncomfortable if not arrested. In addition, low RH increases static electricity for the lack of "lubrication" in the air around things. That state is also critical in this room because there are a lot of electronic devices which may also be affected with the presence of increase static electricity. Lastly, it may seem colder than what is actually the temperature in the room, given that the human body evaporates its fluids faster and therefore lack insulation from the surface temperatures. To address this, mechanical conditioning can introduce heat into the room in order to metabolize the occupants and allow for sweating, which gives off vapors. However, given the actual range of observed temperature, the room can be heated only to about 1 - 2 C more unless the thermal comfort obtained from air temperature will be challenged. The standard recommended range of air temperature discussed in page 5 is less than 27 C and so at the inner portion of the room, the temperature can be raised only by 2 C. An alternative solution is to install a humidifier in the room. It is a home appliance which introduces moisture into the room to help alleviate the symptoms of low RH. US Environmental Protection Agency (2010) cautions against the quality of water being used in the humidifier as impure water can introduce microorganisms and bacteria into the air. The agency recommends the use of distilled water as a safety measure. B. Lighting The laboratory/ computer room lighting source is provided by two sources: ambient lighting from ceiling-height windows and dropped luminaires configured parallel to the white board in the middle of the room. Below is a layout showing the survey on the amount of illuminance on the current space per workstation location: The room presents a wide range of illuminance from 279 - 984 lx. Along North and West walls, the illuminance is lowest while it is brightest at the South wall. It will also be noted that dropped lighting is spread as indicated in yellow rectangles. Upon comparison to the standards, the illuminance at the room is significantly above the required standard, especially taking into consideration that this is a room where VDTs are used. As discussed, an illuminance level of 300 lx should be targeted in the area with special consideration of reducing glare on the computer panels. Since there is ambient natural light coming in, a baseline data on how much illuminance this ambient lighting brings should be taken. This factor is uncontrollable from a mechanical stand point and thus should be an inherent quality of the room that should be considered. Otherwise, the windows can be provided with shutters to completely block out the ambient light and compensate the needed lighting through luminaires. However, from an energy efficiency standpoint, this is a wasteful, thus it is recommended to make use of the available natural light. In addition, since the use of the ambient light is being considered, the room should be re-laid out to position all of the workstations at 90 with the windows. Along the West side of the room, all workstations are at parallel angles with the windows. For those who are facing the window while on their computer, they may have issues with glare from the window. For those whose back are against the window, they maybe finding that the light reflects on their panels and thus are unable to see clearly. From the information gathered on the illuminance of the natural lighting, the luminance should also be taken per workstation. The standard is to achieve 200 candelas per square meter, with a brightness angle of 65 for a category 2 type of use. This can be achieved by using focused angle luminaires that can be set-up to control the amount and the direction of light that falls into a surface. This will require the replacement of the current dropped lighting fixtures. In addition, the current layout of the lighting fixture does not conform to the layout of the workstations. As stated in the standard, the lighting fixture must be in parallel to the computer panel to better control glare. Below is a suggested reconfiguration of the tables (in brown) and lighting fixtures (in yellow): White Board Lastly on lighting, the area where the whiteboard is should be illuminated for adult classroom learning level or 500 lx. This will allow for the rest of the class to view the class lecture from even the West side of the room without having to exert more effort. Currently, there is no focused lighting to highlight the whiteboard. C. Acoustic The current acoustic measurements were taken and resulted as follows: Based on the survey above, the noise level in the room ranges from 55 - 62 dB. This is significantly higher than the target of 35 dB for classroom set-up. Thus, the sources of noise must be addressed. Firstly, the windows and doors must have proper seals in order to reduce the noise that pass through the gaps. Various types of seals maybe used depending on the type of door/ window installed. For the windows, laminated glass windows with acoustic glazing can be installed. In addition, the window reveals should be lined with seals to prevent noise from entering the gaps similar to the example below from Acoustical Surfaces Inc. (n.d.): For doors, seals in between the two panels can be installed to ensure no sound/ noise enters through the gap. Below is a sample of this type of seal from Kestrel Acoustics (n.d.): At the door threshold, a threshold seal should also be installed similar that of Sound Service Ltd (n.d.) as below: Next, the partition walls should also be installed with sound dampening layers to prevent sound from travelling through the hollow partitions. Above the ceiling level, the partitions should be built up to the soffit to ensure that no sound will travel in between rooms at the ceiling level of the partitions. Inside the room, noise can be reduced by introducing materials that absorb noise like fabric, carpet, wood or rubber. One of the walls maybe lined with fabric, say create a bulletin board made of cork that is covered with fabric which can also serve as an absorber of the noise. Carpet is an ideal sound absorber; however, it is not ideal for computer rooms where the possibility of static electricity is present. Recently, manufacturers have developed a line of anti-static carpets, for use in spaces with electronic applications, however, they have stressed the point that the carpet can control the static electricity up to a minimal level and not totally remove it. In addition, this room has a low humidity problem, which will worsen only when carpets are installed. Thus, carpeting is not recommended. What is recommended is anti-static rubber flooring. Rubber is a superior absorber of sound and provides a non-slip surface (Julie Industries Inc. 2010). It is durable for heavy traffic on any weather condition. With the addition of an anti-static circuitry in its design, it is the best option for computer rooms as this. D. Office Design D.1. The Desk As discussed in page 10, minimum desk height should be 720 mm. Adjustable desks are ideal in order to meet the varying height requirements of British adults as indicated in the anthropometry table in page 5. Workspace lateral dimensions must at least be 750 mm wide by 1000 mm deep. This is the average reach of a seated person (Adler ed. 1999, p 11-11). The depth ensures that the keyboard monitor when placed will have at most 500 mm distance from the user, which is the minimum standard. To achieve ergonomic requirements of keyboard placement, keyboard trays must be installed in every desk which allows for 30 - 50mm lower than the top of the work surface. This will ensure that the user will not strain its wrist and elbows from a raised arm while typing. If there will be laptop users in the room, it is ideal to provide a docking station to allow for proper ergonomics. A docking station provides a desktop-type keyboard and monitor so the laptop user will not need to compensate for level and eye viewing limitations of a small computer. This is ideal if the laboratory work lasts at least an hour or so. Under the desk, there must be enough room provided for the seated leg length and possible extension of the legs. Basing from the measurements of British adults, a minimum clearance of 400 mm under the desk is recommended to allow for room for the knees of the 95th percentile of men. D.2. The Chair The lengthy discussion in page 11 can be summed up into two adjectives: fully-adjustable. Ergonomic chairs provide for adjustments of the seat height, back rest height, lumbar support height, back rest tilt, arm rest height and should have the ability to slide the seat forward and backward to compensate for varying length of seated legs. The range of adjustments must be within the 5th percentile of British women up to the 95th percentile of British men. D.3. VDE Regulation Compliance And in compliance with the VDU regulations, the checklist provided should be used for each workstation and address deviations as noted. VI. Summary of Recommendations Below is a summary of the recommendations presented in this paper: 1. The room experiences low relative humidity. Install a humidifier to improve humidity readings and bring it to at least 40% RH; 2. The room is too bright. Install shutters on the ceiling height windows and install controlled-angle luminaires to ensure illuminance of 300 lx and luminance of 200 candelas per square meter on each workstation; 3. The workstation configuration allows for glare and reflection on the VDTs. Reconfigure the workstations to be perpendicular to the windows and reconfigure light distribution to be parallel to the workstations; 4. The room has a high noise level. Install window and door seals to reduce noise from entering the room. Reinforce existing walls with acoustic inserts to prevent noise from travelling through the hollow walls. Install an acoustic wall panel and acoustic floor treatment to absorb noise contained in the room; 5. Replace worktops with adjustable height tables to meet the varied height requirements of the majority of the population; 6. Install docking stations where laptops will be used to allow for ergonomic adjustments as well as prevent strain on the user during prolonged laptop use; 7. Replace chairs with ergonomic chairs that have full adjustments on seat height, slide, backrest height, tilt, lumbar support and arm rest heights; And 8. Use VDU Regulations of 1992 Checklist to check compliance of workstation set-up for each user and address deviations. VII. Conclusion In conclusion, the current computer laboratory presents a lot of opportunity in adhering to standards of ergonomics. The room is currently experiencing low relative humidity, very high noise level, extremely strong illumination and is not equipped with ergonomic furniture. Continuing with the current set-up will impair learning and present physical limitations to the users which may later on turn into injuries if not addressed. As a place of intellectual development, one must also consider that the physical set-up of learning is as important as the intellectual matters discussed in the room. 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