10_work_environment_risks_and_controls_20140117153128

Question 1

Interior lighting can be categorised as

Answer 1

general, localised or local

Question 2

General lighting

Answer 2

Provides uniform illumination over the whole working area and does not limit positioning of the work.

Question 3

Localised lighting

Answer 3

Provides different levels of illumination in different parts of the same working area. It matches the level of illumination to the needs of specific tasks.

Question 4

Local lighting

Answer 4

Usually a combination of background lighting and a luminaire close to the actual work area. Used when:  a high level of illumination is needed in a small area  flexible directional lighting is required for different tasks at a workstation  general lighting is unnecessary or impossible to install because of the layout of the work area

Question 5

Lighting hazards may originate from: 4

Answer 5

 Lighting effects.  Incorrect lighting design.  Improper lighting installation, maintenance, replacement and disposal.  Improper selection of emergency lighting.

Question 6

Hazards from lighting effects

Answer 6

GlareColour effectsStroboscopic effects FlickerVeiling reflections Radiation

Question 7

Field measurements of illuminance may be required for the following reasons: 3

Answer 7

 To establish whether a new installation has achieved the design specification.  To establish whether an installation meets a desired criterion.  For trouble-shooting in identifying the causes of complaints about the lighting.

Question 8

Candela

Answer 8

The candela is the SI (international) unit of luminous intensity. It is equal to one lumen per steradian. Historically one candela was the amount of visible light emitted by one standard candle in a given direction.

Question 9

Lumen (Im)

Answer 9

The lumen is the SI unit of luminous flux, used in describing a quantity of light emitted by a source or received by a surface. The lumen was created as the measure of total luminous power (i.e. visible light power) as defined by a set of ideal human eyes. One lumen is defined as one candela-steradian (cd sr), or the amount of light power needed to send 1 candela of light in all directions.

Question 10

Lux (lx)

Answer 10

The lux (lx) is the SI unit of illuminance, or luminous flux per unit area. It is a measure of the intensity, as perceived by the human eye, of light that hits or passes through a surface. One lux is equal to one lumen per square metre.

Question 11

‘Welfare facilities’ are

Answer 11

those that are necessary for the well-being of employees, such as washing, toilet, rest and changing facilities, and somewhere clean to eat and drink

Question 12

To be readily accessible

Answer 12

the facilities do not have to be within the workplace, but they should, if possible, be within the building. They should be available at all times. The use of public facilities is only acceptable as a last resort, where the provision of better facilities would not be reasonably practicable.

Question 13

It is now against the law to smoke in virtually all ‘enclosed’ and ‘substantially enclosed’ public places and workplaces. Premises are ‘enclosed’ if

Answer 13

they have a ceiling or roof and (except for doors, windows or passageways) are wholly enclosed either on a permanent or temporary basis.

Question 14

It is now against the law to smoke in virtually all ‘enclosed’ and ‘substantially enclosed’ public places and workplaces. Premises are ‘substantially enclosed’ if

Answer 14

they have a ceiling or roof, but have an opening in the walls, which is less than half the total area of the walls. The area of the opening does not include doors, windows or any other fittings that can be opened or shut.

Question 15

It is now against the law to smoke in virtually all ‘enclosed’ and ‘substantially enclosed’ public places and workplaces. The key requirements are that: 4

Answer 15

 Public transport and work vehicles used by more than one person must be smoke-free at all times.  No-smoking signs must be displayed in all smoke-free premises and vehicles.  Staff smoking rooms and indoor smoking areas are no longer allowed, so anyone who wants to smoke has to go outside.  Managers of smoke-free premises and vehicles have legal responsibilities to prevent people from smoking.

Question 16

What is sufficient will depend on the circumstances. A formal assessment of first-aid needs is required to determine the appropriate level of provision. It should consider:

Answer 16

(a) The nature of the work and workplace hazards and risks. The general risk assessment is useful in assessing first-aid needs. Understanding the nature of an accident or injury if preventive or control measures fail can help in determining the necessary first-aid provision. (b) The size of the organisation. A larger workforce generally has a greater the need for first-aid provision. The actual provision should be determined by the risk assessment and assessment of needs. (c) The nature of the workforce. Consideration should be given to the needs of young workers, trainees, pregnant workers and employees with disabilities or particular health problems. (d) The organisation’s history of accidents. In large or multi-site organisations historical accident data may be useful in determining where first-aiders should be located, what area they should be responsible for and what first-aid equipment is necessary. (e) The needs of travelling, remote and lone workers. The assessment should determine the need for the following: (1) Personal first-aid kit. (2) Personal communicators or mobile phone to call for assistance. (3) Additional training. (f) Work patterns. Sufficient provision should always be available when employees are at work. Separate arrangements may be required for each shift, and for ‘out of hours’ working. (g) The distribution of the workforce. On a site with more than one building, if the travel distance between buildings is unreasonable, separate first- aid provision may be required in each building. Numbers and locations of first-aiders or appointed persons in a multi-storey building should give adequate provision to employees on each floor. (h) The remoteness of the site from emergency medical services. Where a site is remote from emergency medical services, special transport arrangements may be required. The emergency services should be informed in writing of the location of remote sites and any particular circumstances, including specific hazards. (i) Employees working on shared or multi-occupied sites. On a shared or multi-occupied site, employers can arrange for one employer to take responsibility for providing first-aid cover for all the workers. (j) Annual leave and other absences of first-aiders and appointed persons. Adequate arrangements for covering both planned absences (for example: annual leave) and unplanned absences (for example: sickness) of first-aiders and appointed person should be made. (k) First-aid provision for non-employees. There is no requirement for employers to provide first-aid for anyone other than their own employees. However, it is strongly recommended that employers include non-employees in their assessment of first-aid needs and make provision for them.

Question 17

Where a first-aider is deemed unnecessary an appointed person may be allocated responsibility to: 3

Answer 17

 take charge of the first-aid arrangements  look after the equipment and facilities  call the emergency services when required.

Question 18

When a candidate is being selected for the role of a first-aider, the following factors regarding their suitability should be considered: 4

Answer 18

 reliability, disposition and communication skills  ability to absorb new knowledge and learn new skills  ability to cope with stressful and physically demanding emergency procedures  normal duties – can they be easily left to respond immediately to an emergency?

Question 19

Thermal comfort is affected by more than just the room temperature. Whether or not a person feels too hot or too cold depends on a combination of:

Answer 19

 Environmental factors, including the air temperature, radiant temperature, relative humidity and air velocity.  Personal factors such as the level of physical activity and the amount of clothing being worn

Question 20

The first classic text on the subject was Thermal Comfort (1970) by Povl Ole Fanger, a Danish scientist. Fanger first recognised that it was the combined effect of the six basic parameters which determines human thermal comfort. Fanger stated that three conditions needed to be met for a person to be in whole body thermal comfort:

Answer 20

(1) The body is in heat balance. (2) The sweat rate is within comfort limits. (3) The mean skin temperature is within comfort limits.

Question 21

The predicted mean vote (PMV) represents

Answer 21

the mean response of a large group of people, in a particular environment, as to how they would rate their ‘thermal sensation’.

Question 22

Thermal balance is obtained when

Answer 22

the internal heat production in the body is equal to the loss of heat to the environment

Question 23

The predicted percentage dissatisfied (PPD) is

Answer 23

an index that establishes a quantitative prediction of the percentage of thermally dissatisfied people, who feel too cool or too warm.

Question 24

The human body operates within a narrow core temperature band between

Answer 24

36.8°C and 37.2°C

Question 25

The heat balance equation may be expressed as:

Answer 25

M + W + K + C + R – E = S M = Rate of metabolic heat production W = External work performed by the body K = Conductive heat loss or gain C = Convective heat loss or gain R = Radiant heat loss or gain E = Evaporative heat loss S = Heat gained or lost by the body

Question 26

Factors Affecting Heat Gain 3

Answer 26

(a) Physical Activity(c) Radiant Heat(b) Air Temperature

Question 27

Factors Affecting Heat Loss 5

Answer 27

(a) Sweating(c) Air Movement(d) Humidity(e) Clothing includingProtective Clothing(b) Acclimatisation

Question 28

Heat stroke is imminent when the core body temperature exceeds

Answer 28

40oC

Question 29

Cold environments Four factors contribute to cold stress:

Answer 29

 cold temperatures  high or cold winds  dampness  cold water

Question 30

Guidance on heat stress from the Australian Institute of Occupational Hygienists (AIOH) highlights the following adverse health effects: 5

Answer 30

 heat stroke  heat exhaustion  heat syncope (fainting)  heat cramps  prickly heat (heat rash).

Question 31

The first effect of excessive heat strain due to cold environments is pain. This is followed by numbness of the extremities, especially the fingers and toes, as the body shunts warm blood to the core, away from the non-vital extremities, such as the hands, feet, nose, cheeks and ears. The effects include: 4

Answer 31

 chilblains  frostbite  immersion foot (trenchfoot)  hypothermia (which may be mild, moderate, or severe).

Question 32

Mild hypothermia

Answer 32

36.5 – 32 °C

Question 33

Moderate hypothermia

Answer 33

32 – 30°C

Question 34

Severe hypothermia

Answer 34

30 – 25.5°C

Question 35

The effects and severity of heat strain on individuals depends on the physiological capacity of the individual, as influenced by the following personal factors: 8

Answer 35

 age  gender  general health (including medical conditions, weight and general fitness etc.)  state of hydration  alcohol, caffeine and diet  nicotine use  medications and non-prescription drugs  acclimatisation and protective clothing and other protective equipment.

Question 36

Thermal surveys - measurement equipment The external variables of interest in determining thermal comfort are:

Answer 36

 air temperature  mean radiant temperature  relative humidity  air flow.

Question 37

The mean radiant temperature is

Answer 37

The mean radiant temperature is the temperature of a uniform enclosure, with which a small black sphere at the test point would have the same radiation exchange as it does with the real environment. Measurement of the mean radiant temperature can be derived from the readings of a black globe thermometer. This consists of a hollow black globe, usually made of copper (due to its high conductivity), in the centre of which is placed a temperature sensor. The standard 150mm black copper globe takes about 20 minutes to reach equilibrium, but this can be reduced by increasing air movement within the globe, and by using thermocouples instead of mercury-in-glass thermometers. Because of its high inertia, the black globe thermometer cannot be used to determine the radiant temperature of environments that vary rapidly.

Question 38

A whirling hygrometer (or sling psychrometer) is commonly used for

Answer 38

determining humidity

Question 39

The whirling hygrometer consists of

Answer 39

two thermometers, a wet bulb and dry bulb. The ‘wet’ bulb is covered with a ‘wick’ or ‘sock’ that has been thoroughly wetted using distilled (de-ionised) water. The hygrometer is swung (like an old football rattle) for about 30 seconds, this allows air movement to pass over the wet bulb thermometer and cause water from the wick to evaporate. After 20 – 30 seconds, the aspirated wet bulb temperature is read first, followed by the dry bulb temperature. These values are noted and the measurements repeated three times. From the dry bulb and aspirated wet bulb temperature it is possible to calculate the partial vapour pressure (P a ), relative humidity (RH) and dew point (t dp ) or determine the relative humidity via a psychrometric chart At 100% relative humidity (saturation) there will be no depression of the aspirated wet bulb temperature.

Question 40

As air movement varies in time, space and direction it is the ‘mean’ air velocity over the body, integrated over all directions and over an exposure time, that is of interest. Air velocity can be measured by: 3

Answer 40

 hot-wire anemometer  vane anemometer  kata thermometer.

Question 41

The hot-wire anemometer works by

Answer 41

an electrical current heating the sensor to a temperature above ambient, and being cooled by air movement. The amount of cooling is dependent on the air velocity, the ambient air temperature and the characteristics of the heat element. These devices are directional and can be inaccurate in low air velocities due to natural convection of the hot wire.

Question 42

The rotating vane anemometer consists of

Answer 42

a number of blades that are configured to allow the air movement to rotate them in one direction. The number of rotations are then counted over a period of time (usually 1 minute) and converted to air velocity. These devices are not accurate at low air velocities, are not omnidirectional and cannot be used where the direction of airflow is variable.

Question 43

The kata thermometer consists of

Answer 43

a silvered bulb that has two levels marked on the thermometer, corresponding to a temperature drop of 3°C. The thermometer is heated to above the temperature of the upper graduation, wiped dry and allowed to cool while still clamped in place. The time taken to cool over the marked temperature interval is measured. Air velocity may then be derived by formula or nomogram (graphical representation of numerical relations) from three known quantities, i.e. the cooling time, the dry bulb temperature of the air, and a calibration factor for the particular kata thermometer, which represents the heat loss per unit surface area as the thermometer cools.

Question 44

Heat stress indices typically fall into two types:

Answer 44

empirical indices and theoretical rational indices.

Question 45

Empirical indices have been developed by assessing the physiological effects on a test group of people under varying environmental test conditions, and include: 4

Answer 45

 Effective temperature (ET).  Corrected effective temperature (CET).  Predicted 4-hour sweat rate (P4SR).  Wet bulb globe temperature (WBGT).

Question 46

Theoretical or rational indices are derived by

Answer 46

consideration of the effects of the environment on the body’s heat balance. An example of a theoretical or rational indices is the Heat Stress Index (HSI), which was modelled on the heat balance equation, and is based on a comparison of evaporation required to maintain heat balance with the maximum evaporation that could be achieved in that environment.

Question 47

The Effective Temperature Index (ETI)

Answer 47

combines the effects of air temperature, humidity and air movement into one scale to be used as a basis for comparisons.

Question 48

Corrected Effective Temperature Index (CETI)

Answer 48

As the ETI did not take into account the effects of radiant heat, it was later modified to form the Corrected Effective Temperature Index (CETI). The basis for this index was to use a 150mm diameter black globe thermometer measurement (radiant heat) on the scale, in place of the dry bulb reading (air temperature).

Question 49

The predicted 4-hour sweat rate (P4SR) index

Answer 49

measures sweat rate as a function of climate stress, and uses a nomogram to predict the quantity of sweat given off by fit, acclimatised young men exposed to the environment for four hours.

Question 50

Wet bulb globe temperature (WBGT) values are calculated from one of the following equations:

Answer 50

With direct exposure to sunlight (outdoors) WBGT out = 0.7 NWB + 0.2 GT + 0.1 DB Without direct exposure to the sun (indoors) WBGT in = 0.7 NWB + 0.3 GT

Question 51

The heat stress index (HSI) is

Answer 51

a comparison of evaporation required to maintain heat balance (Ereq), with the maximum evaporation that could be achieved in that environment (Emax). HSI = Ereq \ Emax x 100

Question 52

Engineering controls can be an effective way of reducing heat stress and preventing or minimising occurrence of heat illness. Examples include: 9

Answer 52

 Increasing air movement using fans.  Installing shade structures to reduce radiant heat from the sun.  Installing shields or barriers to reduce radiant heat from sources such as furnaces or hot vessels.  Removing heated air or steam from hot processes using local exhaust ventilation.  Insulating indoor workplaces.  Installing air conditioners or coolers to reduce air temperature.  Locating hot processes away from people.  Insulating /enclosing hot processes or plant.  Using mechanical aids to reduce physical exertion.

Question 53

Management controls Heat stress can be reduced by attention to the way work is organised, for example: 6

Answer 53

 Rescheduling work so the hot tasks are performed during the cooler part of the day, or in cooler times of the year.  Reducing the time an individual spends doing the hot tasks, for example: by job or task rotation.  Arranging for more workers to do the job.  Making sure there is easy access to cool drinking water.  Providing additional rest breaks in cool, shaded areas.  Providing training and information to enable workers to: - identify hazards - recognise symptoms of heat stress and heat illness - understand how to avoid heat illness.

Question 54

Suitable clothing and PPE may help to further reduce the risk of heat illness, for example: 4

Answer 54

 broad brimmed hat  appropriate protective clothing to cover workers at least between elbow and knee, however long sleeves and trousers provide the best protection  sunscreen  sunglasses.

Question 55

As wind chill is the most critical factor in the onset of cold stress, engineering controls that reduce exposure to the wind are useful. The two common approaches are:

Answer 55

 Wind barriers (shields) which can be effective outdoors or against circulated air indoors in freezer rooms.  Refuges, which are warm areas equipped with warm drinks, so that workers can retreat to rest. The ideal is for the required task to be performed inside the refuge.

Question 56

Other engineering controls for cold stress include: 6

Answer 56

 Avoiding metal tools and thermally insulating metal handles and bars.  Provision of local heating.  Mechanical aids to reduce manual handling requirements (and the potential for perspiration).  Designing machines and tools to be operated without having to remove mittens or gloves.  Designing workplaces so that operators are not required to sit or stand for long periods in cold conditions.  Reducing air velocity in cool rooms / chillers while workers are required to work inside.

Question 57

Management controls for cold stress 10

Answer 57

 Monitoring of air temperature, air velocity and equivalent chill temperature.  Work-rest schedules with adequate rest breaks to warm up between periods of moderate to heavy work activity.  Information and training about the symptoms of adverse health effects from exposure to cold and suitable precautions.  Medical screening of workers. Workers who are suffering from respiratory or cardiac diseases or taking medication which interferes with normal body temperature regulation should be excluded from work in cold environments.  Acclimatisation periods. An acclimatisation period of around one week is recommended for new workers. Extra attention should be paid to those returning to work after an extended absence from cold exposure situations due to illness.  Supervision to monitor for signs and symptoms of workers exposed to potentially hazardous cold conditions.  Self-reporting of illness, medication, alcohol intake and other factors that may influence susceptibility to cold stress.  Self-paced working at temperatures below -12°C. Work rates should not be so high as to cause heavy sweating that will result in wet clothing.  Encourage healthy life-styles. A good diet and physical conditioning help protect against abnormal cold. Nicotine and alcohol should be avoided.  Administrative controls for arranging work in such a way that sitting still or standing still for long periods is minimised. Where possible work should be scheduled for the least cold part of the and long shifts, and excessive overtime should be avoided in the cold.

Question 58

Effective Temperature Index (ETI)

Answer 58

The Effective Temperature Index (ETI) combines the effects of air temperature, humidity and air movement into one scale to be used as a basis for comparisons. The ETI uses the concept of the temperature of a standard environment as the index value. It is the temperature of a standard environment that contains still, saturated air that would provide the same sensation of warmth as in the actual environment.