LIGHTING AT WORK PLACE

Kwok Ngai Kan ES00090

The benefits of proper lighting To allow employees to comfortably see

what they’re doing, without straining their eyes or their bodies

To make work easier and more productive

To draw attention to dangerous operations and equipment

To help prevent costly errors and accidents

Definition of illuminance

To know what is the suitable lighting for the workplace, we should define some terms.

‘luminous flux’ is the flow rate of light energy and the unit is ‘lumen (lm)’

‘illuminance’ - density of light shining onto a surface

‘illuminance’ is measured as: 1 lm/m2 = 1 lux (lx) [SI unit] 1 lm/ft2 = 1 foot-candle (fc) [US unit]

Here is the recommended lighting levels by different tasks and area

To assess whether lighting is sufficient in your workplace, consider these factors:

1. Human factors 2. Area to be lit 3. Tasks to be done 4. Equipment and furniture used in tasks

1. Human factors

The lighting should be sufficient and comfortably to the employees to do their work

Insufficient light → visual fatigue and discomfort → lower the work productivity and efficiency

To solve this, we can use some lighting with adjustable intensity.

2. Area to be lit furniture and partitions can block

general lighting overhead lights can create shadows

which can make work difficult and even dangerous by hiding sharp edges and other potential hazards

3. Tasks to be done The amount of light a worker needs depends on the

tasks to be done.

E.g. The light required in factories such as making electronic chips is more than the light required in a office work.

There are four factors affecting the visibility of object:

- its size

- contrast between the object and its background

- time available to view the object

- its brightness

Size- The bigger the object, the easier it is to see.

Contrast- Low contrast makes it difficult to distinguish

an object from its background.- E.g. Orange and Black

Time

- Time is needed for eyes to focus on and evaluate an object.

- Give more time to the employees who work with small pieces

Brightness

- The brighter an object is, the easier it is to see

Glare

There are two main types of glare: direct and reflected (or indirect).

Direct glare occurs when a source of bright light is directly in an employee’s field of view

Reflected glare is caused by light that reflected by surfaces into the worker’s eyes.

Equipment and furniture the type of lighting needed depends on

the equipment and furniture used E.g. some lighting is more noticeable on

large surfaces that are highly reflective.

Case Study- Impact of lighting arrangements and illuminance on different impressions of a room

To investigate how the qualitative aspects of space (the impressions of a space) could be enhanced with lighting.

Hypotheses

1. Different lighting arrangements effect impressions of people about a room.

2. Different illuminances of the same lighting arrangement affect impressions of people about a room.

Experiment set-up Room : 4m x 4m with height 3m No windows > no effects of daylighting Grey terrazzo tiles floor with 0.2 luminous reflectance Blue door with 0.3 luminous reflectance White ceiling with 0.79 luminous reflectance A observation table was located at one corner as the

observation table Participants : 40 male and 60 female

Lighting arrangements : uniform lighting, cove light and wall washing

Lighting : 500 lux (high) and 320 lux (low)

Participants were seated at the observation table. They need to fill in the questionnaire.

The participants were asked to select the most suitable lighting arrangement for each impression and compare the two illuminances (500 and 320 lux) for the lighting arrangement.

Here is the questionnaire.

Result Using Chi-square test to find out whether there is a

significant relationship between the lighting arrangements (general lighting, cove lighting and wall washing) using p-value.

p-value is the probability of obtaining a test statistic at least as extreme as the one that was actually observed

For each pair of lighting arrangements on each impression, proportion (p) of preferences was tested using single-sample proportion test for large samples. In all these tests:

Ho : p =1/2, Ha : p >1/2.

general lighting more than cove lighting (p-value =0.0002)

Wall washing more than cove lighting(p-value =0.0002)

No significant difference between preferring general lighting and wall washing (p-value =0.9204).

High level (500 lux) is preferred for both general lighting and wall washing (p-value = 0.0002 for each).

Clarity

Spaciousness

wall washing more than general lighting ( p-value = 0.0178)

wall washing more than cove lighting (p-vlaue = 0.0002)

High level (500 lux) is preferred to enhance spaciousness (p-value = 0.0002)

Relaxation

Cove lighting more than general lighting (p-value =0.0002)

Cove lighting more than wall washing (p-value = 0.0096)

To enhance relaxation, low level (320 lux) of cove lighting is preferred (p-value = 0.0016).

Privacy

Cove lighting was preferred more than general lighting (p-value =0.0002)

Cove lighting was preferred more than wall washing (p-value =0.0002).

Cove lighting was preferred to be a low lighting level (320 lux) to achieve privacy (p-value =0.0002).

Pleasantness

Cove lighting is preferred (p-value = 0.0002) and wall washing (p-value = 0.0002) over general lighting,

no significant difference between preferring cove lighting and wall washing (p-value =0.215)

As p-value = 0.6242 for cove lighting, p-value =0.215 for wall washing, people enjoyed both illuminances

Order

Wall washing was preferred more than general lighting (p-value =0.0016) and more than cove lighting (p-value =0.0002).

high illuminance level(500 lux) is preferred to achieve visual order (p-value =0.0038).

Conclusion

Hypotheses 1 is right as different lighting arrangement s affect impressions of people about a room

Hypotheses 2 is also supported as there is a statistically significant difference between the number of people preferring high and low levels of illumination for the lighting arrangements they chose for a specific impression

So wall washing and cove lighting were preferred to convey different impressions in this study.

Wall washing was associated with the impressions of clarity, spaciousness, pleasantness and order

Cove lighting was associated with relaxation, privacy and pleasantness.

Wall washing was always preferred to be at high illuminance (500 lux)

Cove lighting to be at low illuminance (320 lux)

END