Occupational Health Tools 2009
Physical hazards
Six factors that affect feelings of warmth
Air temperature
How hot or cold the air around us is. It is what we measure with a thermometer. It will have a direct warming or cooling effect on a person. In situations with a high radiant heat level, air temperature alone is not a good indicator of the thermal environment.
Humidity
The moisture content of the air. The warmer the air, the more moisture it is able to carry. High humidity tends to make people feel hotter than low humidity. This is because a person’s sweat will not evaporate and cool the person as the air is already moisture saturated. Cold air has a lower moisture content, so humidity is not a factor in cold environments, except that mist, rain or wet clothing can cause a decrease in insulating characteristics.
Radiant heat
Is emitted from anything that is hot. Radiant heat will in time heat the air, but people will absorb heat directly far more quickly. Radiant heat will affect people anywhere there is direct sunlight, or where a person is close to a process that emits heat.
Air speed
In most situations will cool a person. This will provide some relief to people in a hot situation, but extra chill to people in a cold situation.
Physical activity
Will increase the generation of heat in the body. In a cold environment, physical activity can help to warm a person. In a warm or hot environment, physical activity can increase the load of heat on a person. A high level of physical activity on a hot day can place a worker at risk of heat strain.
Clothing
Aids or prevents heat transfer from our bodies to the surrounding environment. In a cold environment, a person should wear clothing that will prevent as much heat transfer as possible. Ideal clothing in a hot environment will allow a worker to freely dissipate heat.
Heat strain
| Key questions | Key points |
|---|---|
| What is the progression of symptoms in response to exposure to heat? | Mental: Irritation, anger, aggression, depression Physical: Sweating, increased heart rate Early symptoms: Headaches, muscle cramps, changes in pulse and breathing rate, weakness, heavy perspiration, prickly heat, feeling faint, reduced performance Later symptoms: Severe headaches, increased irregularity in pulse and breathing, severe muscle cramps, confusion, cold, clammy skin and cessation of perspiration. |
| What health conditions are associated with exposure to heat? | Dehydration: The main signs of this are not passing urine and changes to mental state and personality. Heat syncope: Fainting – results from a drop in blood pressure during prolonged standing or sitting in heat. Heat rashes: 3 types occur and may be made worse by 20 infections. Prickly heat (most common) occurs where clothing is restricted. Heat cramps: Occur in muscles when the salt balance is disturbed. Alleviate by rest, drinking water, and salt intake. Heat exhaustion: Linked to depletion of body fluids and electrolytes. Heat stroke: Least common but most serious. It causes central nervous system effects (convulsions, mania or coma, dilated pupils and a hot, dry skin). Rapid treatment is essential. |
| When are these likely to occur? | The more the person works hard, is exposed to high air temperatures, high humidity, high levels of radiant heat and wears heavy clothing, the more likely these symptoms are to occur. |
| Assessment | To assess the heat load on a person use the WBGT Index – the wet bulb – globe thermometer index. Consult a hygienist. |
| How can heat strain be prevented? | lower the air temperature, humidity and radiant temperature increase the air speed (fans, ventilation systems) control activity timing (time of day, take breaks, spell the work) wear sunhat, suitable clothing - loose and thin but covering skin replace water lost through sweating shield radiant heat sources work in the shade – provide shade shelters use administrative controls (job rotation). |
| What treatment? | Heat stroke can be rapidly fatal. Where planning for work in hot environments, a first-aider with special knowledge of heat conditions will be required – in anticipation of emergencies. |
Cold strain
Progression of symptoms in response to exposure to cold
| Mental: | Alertness reduced. |
| Physical: | Sensitivity and dexterity of fingers reduced. |
| Frost nip: | Blanching of fingers, toes, ears, cheeks and nose. |
| Frostbite: | Occurs when blood circulation ceases due to frozen skin/tissues. Patchy skin inflammation and slight pain ranging to painless tissue damage; and the skin becomes prone to infection and gangrene. |
| Trench foot: | Occurs when feet are exposed to long periods of immersion in water – damage to nerve and muscle tissues. |
| Hypothermia: | The culmination of a set of experiences leading through sensations of cold, shivering, pain in exposed parts of the body, increasing numbness, decreasing pain, weakness and drowsiness, cessation of shivering, diminished consciousness and dilated pupils. |
Progression of cold strain – core temp. and corresponding symptoms
| Temp. (°C) | Symptoms |
| 37.5 | Normal core (rectal) temperature |
| 37 | Normal oral temperature |
| 36 | Metabolic rate increases to compensate for heat loss |
| 35 | Maximum shivering |
| 34 | Victim conscious and responsive, with normal blood pressure |
| 33 | Severe hypothermia from here |
| 31-32 | Consciousness clouded, blood pressure difficult to get, pupils dilated |
| 30-29 | Progressive loss of consciousness, muscular rigidity increases, pulse and blood pressure difficult to obtain, respiratory rate decreases |
| 28 | Ventricular fibrillation possible |
| 27 | Voluntary motion stops; pupils non-reactive to light; reflexes absent |
| 26 | Victim seldom conscious |
| 25 | Ventricular fibrillation may occur spontaneously |
| 24 | Pulmonary oedema |
| 22-21 | Maximum risk of ventricular fibrillation |
| 20 | Cardiac standstill |
| 18 | Lowest accidental hypothermia victim to recover |
| 17 | Brain waves stop |
| 9 | Lowest recovery temperature |
Assessing risks:
To find out the effect of the combination of air temperature, wind speed and physical activity, consult tables 6 and 7 on pages 52 and 53 of the Guidelines for the Management of Work in Extremes of Temperature to obtain a measure called ‘equivalent chill temperature’ or ECT.
Monitoring:
Use a suitable thermometer where the air temperature may drop below 16°C. In workplaces where the temperature is below freezing (0°CECT), and/or the speed of air movement is greater than 2 m/sec, the temperature should be monitored at least every 4 hours.
Emergency procedures:
Provide for an adequate fi rst aid response. Preventing cold strain For continuous work in low temperatures, heated warming shelters, such as cabins and rest rooms, should be provided. The level of activity should not be great enough to produce excessive sweating. If excessive sweating is likely to occur, or it involves working in the wet, facilities should be available for changing, or for drying clothes and footwear. Work environment: Shield workers from drafts and winds.
Equipment design:
Metal handles and bars should be thermally insulated. Tools and equipment should be designed so that they can be operated without removing gloves.
Clothing:
Wear protective clothing where work is done at temperatures below 4°C wind chill temperature. Select clothing to suit the temperature, the nature of the work, and the activity level. Clothing in multiple layers is better than a single thick layer.
In wet conditions:
Outer layers of clothing should be water repellent.
In windy conditions:
Wear clothing designed to prevent wind penetration.
Hand protection:
If fine work needs to be performed with bare hands for more than 10-20 minutes at temperatures below 16°C, take special precautions to keep the hands warm, for example, by providing warm air blowers and insulated handles on tools. If fine manual dexterity is not required, gloves should be worn for:
- Sedentary work < +10°C
- Light work < +4°C
- Moderate work < -7°C
- Below -170C, mittens should be worn.
Footwear:
Felt-lined, rubber-bottomed, leather-topped boots with removable thermal insoles are best suited for work in cold environments.
Head covering:
A head covering, such as a woollen cap or a hard hat with a thermal liner, should be worn in cold environments, as over 50% of heat loss is through the head.
General safe work practices
- Do not allow bare skin to come into contact with cold surfaces below -7°C, especially surfaces made of materials that are good conductors of heat, e.g. metals.
- Do not allow bare skin to come into contact with evaporative liquids, e.g. petrol, cleaning fluids, alcohol.
- Do not stay still for a long time.
- Do not consume alcohol.
- For warming purposes, supply hot non-alcoholic drink. Limit caffeine consumption as it increases urine production and blood circulation – both increase the loss of body heat.
- Restrict tobacco consumption.
- Eat adequate food frequently.
- Drink plenty of water to rehydrate.
- In refrigerated rooms, keep air speed < 1 m/sec where possible.
- All work in cold conditions should be under constant observation (through a buddy system or supervision).
- New employees and workers should not be required to work full-time in the cold until they have become accustomed to the conditions and the personal protective clothing they need to wear.
- Apply lip balm and moisturising lotions to prevent lesions.
- Maintain a high level of fitness.
- If a worker cannot be adequately protected from the effects of cold, then work must be suspended, or work regimes modified, to remove the risk of harm.
Thermal Comfort
Thermal comfort is a condition of the mind which expresses satisfaction with the thermal environment. Thermal discomfort is the uncomfortable place between an environment that is ideal and one that will cause harm (through heat stress or cold stress).
Conditions in which most people will be thermally comfortable – for sedentary and active occupations.
| Condition | Summer value | Winter value |
|---|---|---|
| Air temperature (°C) | 19-24 | 18- 22 |
| 16-21 (active work) | 16-19 (active work) | |
| Relative humidity | 40-70% | |
| Air speed | 0.1-0.2 m/s, no draughts up to 0.5 m/s (active work) | |
| Radiant heat | No direct exposure to a radiant heat source | |
| Clothing | Light clothing | Winter clothing |
Thermal discomfort: This may not cause an immediate safety or health problem but may affect morale, feelings of tiredness and irritability which may lead to reduced production. As thermal discomfort increases the line between safe and unsafe conditions becomes more and more blurred. Judgement will be needed to decide when conditions become unsafe. In buildings, thermal discomfort may occur when a ventilation system is not able to provide enough heating (in winter), cooling (in summer when sunshine through large windows adds a large heat load) or air movement.
Lighting – merits and demerits of various luminaires
| Type | Advantages | Disadvantages |
|---|---|---|
| Spotlights | Spotlights add interest to the appearance of the lighting and can give high light levels. They are good to use to with flush-mounted fluorescents as ‘wall washers’ or with up-lighters to add ‘sparkle’. | They create shadows on faces and cast shadows. They can cause glare, especially in VDU screens, if not positioned properly. |
| Up-lighters (light reflected off ceiling): | Up-lighters do not cause glare in VDU screens or act as sources of direct glare. They create a diffuse, even illumination. Can be portable. | The appearance of their lighting is bland. Ceilings must be a highly reflective white colour. They are difficult to design, to avoid ‘hot spots’ on the ceiling. |
| Local lighting | They allow fi ne control of the light distributions on a desk, but only if the geometry of their light control surfaces is good. They allow lower levels of ambient light to be used, which may result in reduced glare. | They may emit heat. They may cause glare. They are difficult to design so that the illumination they cast on a desk is evenly distributed. |
| Flush mounted fluorescents | The right sort of grid in the luminaire can result in very good lighting for VDUs, if they throw light downward at an acceptable cut-off angle of 45-60°. | If the cut-off angle is large they may produce glare. The ceiling and walls are not lit, which may create gloomy feelings. They can be expensive to run if close set grids intercept much of the light output. |
| Surface mounted fluorescents | These luminaires can light the ceiling and walls. They are best used when there are high ceilings (and are thus out of the normal line of sight.) | They can create severe glare, especially if naked tubes are not shielded properly, if they hang in rows on a ceiling, or if there is a low ceiling. |
| Pendant fluorescent luminaires | They throw light upwards and downwards and light the ceiling and walls. When designed well, and when supplemented by other luminaires, they give the best lighting for VDU. | Pendant luminaires are severe sources of glare if not designed as described. |
| Incandescent bulbs | The familiar light bulb creates a warm appearance. | Can cause intense glare as the light emitted per unit area is very large. They have no place in the office except in shielded local lighting. |
An abbreviated approach to lighting
| Key concepts | Key principles |
|---|---|
| Why bother with lighting? | for task clarity and general safety for ease of mobility to provide a faithful appearance of the form and shape of objects, spaces, people and faces for visual comfort to create a mood for clear communication. |
| There is a lot more to lighting than just getting the amount ‘right’ | It is important to have enough light on the scene. BUT . . . That’s not the end of the story. Equally important are: the type of lamp the type of luminaire the décor control of daylight the people discomfort or disability glare colour of the source lighting directionality. |
| Getting the amount right | To find out how much light you need on a task you need to know: the difficulty of the task how long it goes on for visual status of workers consequences of errors. See the sample calculation on the next page |
| Lighting for safety | A uniform distribution of light is needed for safety and to reduce visual fatigue. (e.g. there should not be big contrasts in the amount of light in a space). Stairs, ladders, aisles, passageways, exits and outside areas all need to adequately lit. Use intrinsically safe fittings with flammable substances. Fluorescent lighting with moving/rotating machinery can cause difficulties because of the stroboscopic effect. |
Glossary
Lamp: A light-emitting device (bulb, fluorescent tube, metal halide etc.)
Luminaire: The lamp - its mounting and light control surfaces (e.g. a flush-mounted or pendant fluorescent or an up-lighter) - see previous page.
Directionality: Light can flow in a straight line (as from a spotlight) or be every which way equally (like on a cloudy day).
Calculating the amount of light needed
Calculating the amount of light: For the task of pouring molten gold into an intricate casting: start with the standard service illuminance (See New Zealand Standard 6703:1984). For this task it is 300 lux. Now make four corrections according to the standard decision flowchart:
| The task is difficult | - add 200 lux | - 500 lux |
| It is done for only 30 minutes per day | - subtract 200 lux | - 300 lux |
| The consequences of errors are high | - add 200 lux | - 500 lux |
| Operators have normal visual status | - No correction | - 500 lux |
| Final result: 500 Lux | ||
Lamps: Different lamps are suitable for different applications because of their brightness, efficiency or colour rendering properties (e.g. halogens lamps render colours superbly).
Luminaires: Apart from selecting the right type, they need to put in the right place on the ceiling. Maintain them by regular cleaning and re-lamping to maintain their efficiency.
Décor: Walls and ceilings all emit light by reflection - so the decor must be regarded as part of the lighting system. Colour influences mood. Reflective light surfaces (which implies light or pastel colours) make for lighter spaces. To reduce reflections, use dark colours.
Daylight control: Sunlight entering windows can cause glare or reflections in VDU screens or an increased heat load. Use appropriate window treatments to control daylight – there is a lot of detail in this topic, so seek specialist advice.
Glare: Glare is of two kinds –
- Disability - you are dazzled by a bright light in the field of view, e.g. while driving or using a computer screen with the sun visible behind it through a window.
- Discomfort - glare makes it more difficult to do the task, e.g. bright pinpoint reflections of overhead metal halide lamps in the stainless steel of the conveyor housing means that your task of inspecting kiwi fruit is made more difficult. Solutions are obvious.
Directionality: To reveal the three-dimensional (3-D) nature of objects, spaces, people and faces – for – safety, the ease of use of things and for clear communication, there needs to be a mix of directed light (e.g from a spotlight) and omnidirectional light (e.g. as in a cloudy day). Think of trying to work out what a person’s face is ‘saying’ if it is either lit from directly above by a single spotlight or outside on a dull day. When the 3-D nature of a person’s face (body language) is revealed, communication is easier.
The current Standards: AS/NZS 1680.1:2006 Interior lighting - General principles and recommendations.
The publications page of the Chartered Institute of Building Services Engineers website at www.cibse.org and the Society of Light and Lighting are well worth visiting.
Noise
Excessive noise exposure can cause Noise Induced hearing loss (NIHL).
Noise-induced hearing loss is a permanent condition of the inner ear characterised by loss of hearing ability particularly in the voice recognition range.
Noise-induced hearing loss is a major cause of disability and compensation in New Zealand.
The extent of noise-induced hearing loss (NIHL) depends on the intensity of the noise, its duration and its frequency (or pitch). Put simply, the more time a person’s ears are exposed to excessive noise, the greater the degree of hearing loss. More time equals more acoustic energy and hence more damage. The damage that results is irreversible, and treatment is limited.
Some individuals are more sensitive to noise than others and will lose hearing more readily through noise exposure. The large variations in the susceptibility of individuals to hearing damage due to exposure to excessive noise means that the exposure limits set out in the regulations are therefore not in themselves guaranteed to remove all risk of noise-induced hearing loss.
Regulation 11 of the Health and Safety in Employment regulations requires employers to take all practicable steps to ensure that no employee is exposed to noise above either/both of the following:
An average of 85 decibels over 8 hours (A-weighted measurement);
A peak level of 140 decibels (un-weighted measurement).
Notes:
- This standard also applies if the worker is wearing hearing protection.
- Just because someone is exposed to noise above 85 decibels for a short period during a shift does not mean their exposure exceeds the 8 hour standard. This is because the 8 hour standard is based on average exposure.
- The standard for people working longer shifts than 8 hours is less than 85 dB(A) average. For a 12 hour shift the Standard is 83 dB(A).
Preliminary noise measurement can be carried out by any person with no special training in noise however this is only a very basic assessment. The noise code of practice provides guidance on this type of assessment. A detailed assessment to determine if: noise control, hearing protection or audiometry is required should be done by a competent person using specialised monitoring equipment.
References:
- Approved Code of Practice for the Management of Noise in the Workplace
- Health and Safety in Employment Regulations, 1995. Section 11
Summarising the Approved Code for Noise
| Key principles | Key actions | Key tools and references |
|---|---|---|
| Provide a safe place of work | Take all practical steps to ensure that no employee is exposed to noise in excess of the exposure limits. | See the Approved Code of Practice for the Management of Noise in the Workplace – section 2.2 ‘Providing a Safe Place of Work’. |
| Identify noise hazards | Carry out a preliminary noise survey to identify possible noise hazards. If any present then assess their significance as below. | This does not need to be done by a ‘competent’ person. See the Approved Code of Practice for the Management of Noise in the Workplace - section 3 ‘Preliminary Noise Surveys’. |
| Assess their significance | Every 5 years - arrange for a detailed noise survey to be carried out to assess the significance of noise hazards. | This must be done by a ‘competent’ person. See the Approved Code of Practice for the Management of Noise in the Workplace - section 4 ‘Detailed Surveys–Assessing Noise Hazards”. |
| Control significant hazards by elimination, isolation, or minimisation | If practicable, eliminate noise at source. If not, isolate noise sources. Provide hearing protectors when noise hazards can’t be eliminated or isolated, and while work is being carried out to control noise at source. Also monitor exposures to noise – when processes change or are added, for example. | See the Approved Code of Practice for the Management of Noise in the Workplace - section 7 ‘Reducing Noise in the Workplace’. See the Approved Code of Practice for the Management of Noise in the Workplace - section 6 ‘Reducing Noise Exposure With Hearing Protectors’. |
| Monitor the health of employees | Arrange for hearing tests (audiometry) to be carried out on all employees who work in an area with hazardous noise – when an employee starts work, and at intervals of no longer than 12 months thereafter. | This must be done by a ‘competent’ person. The Department of Labour must be notified if an employee has a hearing loss that meets the Department’s criteria. See the Approved Code of Practice for the Management of Noise in the Workplace - section 7 ‘Monitoring the Health Effects if Noise’. |
| Provide information, training and supervision | Provide information to employees on noise hazards. Provide training and/or supervision to employees in the safe use of plant or use of hearing protectors. | See the Approved Code of Practice for the Management of Noise in the Workplace - section 8 ‘Training and Education’. |
Vibration
| Key principles | Key actions |
|---|---|
| Provide a safe place of work | Hand-arm vibration can cause injuries and disease to the hand and arms ranging from vibration white finger (Reynaud’s disease), up to hand-arm vibration syndrome (HAVS) – through effects on the blood circulation system. Identify hazards Carry out a preliminary survey to identify sources of whole body and hand-arm vibration. |
| Assess their significance | If necessary, arrange for a detailed survey to be carried out to assess the significance of hazards. |
| Control significant hazards by elimination, isolation, or minimisation. | If practicable, eliminate vibration at source. If not, isolate vibration sources. See opposite page. |
| Monitor the health of employees. | Arrange for medical examinations to be carried out on all employees who face a significant hazard from exposure to vibration. |
| Provide information, training and supervision. | Provide information to employees on identified vibration hazards. Provide training and/or supervision to employees in the safe use of plant or use of equipment, tools etc. |
Exposure: There is a potential for exposure when using any powered hand tool (e.g. nut runners, pneumatic breakers, angle grinders); or working with any powered machinery (e.g. a lathe). The risk clearly depends on the length of time the person is exposed for.
Avoiding whole-body vibration in vehicles:
Employer: Construct designated access-ways and keep them smooth. Maintain vehiles
Driver: Drive slowly; adjust the seat properly; get the seat repaired, if necessary; clean the windscreen; adjust the mirrors properly; inflate the tyres properly; keep to the designated smooth access-ways.
Vibration Controls
Key ideas and controls
White finger, or Raynaud’s disease, is a disease of the hands in which the blood vessels in the fingers collapse due to repeated exposure to vibration. The skin and muscle tissue do not get the oxygen they need and eventually die.
Hand-arm vibration syndrome (HAVS) is a more advanced condition, and the entire hand or arm may be affected by exposure to vibration. Early signs of HAVS are infrequent feelings of numbness and/or tingling in the fingers, hands, or arms, or numbness and whiteness in the tip of the finger when exposed to cold. As the disease progresses, a worker experiences more frequent attacks of numbness, tingling, and pain and finds it difficult to use his or her hands. A worker with advanced HAVS may be disabled for a long period of time.
Engineering controls
- vibration isolators or damping techniques on equipment offer the most effective protection
- vibrations of the panels of machine housings and guards may be controlled by the use of damping materials applied to the panels. Felts, liquid mastics, and elastomeric damping sheets are effective damping materials
- determining the correct type and quantity of damping material to use for a particular machine is a complicated process and should be left to a knowledgeable person. The frequency generated by the machine, the reduction desired, and the weight and size of the machine are factors to consider
- a good rule of thumb, however, is that the damping layer should be the same thickness as the surfaces being treated.
Work practices
- maintain machines in proper working order
- unbalanced rotating parts or blunt cutting tools can cause excessive vibration
- arrange work tasks so that vibrating and non-vibrating tools can be used alternately
- restrict the number of hours a worker uses a vibrating tool during the workday
- allow employees to take 10 to 15 minute breaks from the vibration every hour
- train workers about the hazards of working with vibrating tools. Instruction should include: the sources of vibration exposure; early signs and symptoms of hand-arm vibration syndrome; and work practices for minimizing vibration exposure. Instruct workers to keep their hands warm and dry, and not to grip a vibrating tool too tightly. Workers should allow the tool or machine to do the work.