Effects depend on the duration and intensity of exposure and to some extent, upon the individual's natural reflex action to close the eye and exclude the incident light. Normally this dazzling does not produce a long-term effect.
Infrared radiation
Infrared radiation is of longer wavelength than the visible light frequencies, and is perceptible as heat. The main hazard to the eyes is that prolonged exposure (over a matter of years) causes a gradual but irreversible opacity of the lens.
Fortunately, the infrared radiation emitted by normal welding arcs causes damage only within a comparatively short distance from the arc. There is an immediate burning sensation in the skin surrounding the eyes should they be exposed to arc heat. The natural human reaction is to move or cover up to prevent the skin heating, which also reduces eye exposure.
BS EN 169 specifies a range of permanent filter shades of gradually increasing optical density which limit exposure to radiation emitted by different processes at different currents. It must be stressed that shade numbers indicated in the standard and the corresponding current ranges are for guidance only.
11.4 Fumes and gases 11.4.1 Fumes
Because of the variables involved in fume generation from arc welding and allied processes (such as the welding process and electrode, the base metal, coatings on the base metal and other possible contaminants in the air), the dangers of welding fume can be considered in a general way. Although health considerations vary according to the type of fume composition and individual reactions, the following holds true for most welding fume.
The fume plume contains solid particles from the consumables, base metal and base metal coating. Depending on the length of exposure to these fumes, most acute effects are temporary and include symptoms of burning eyes and skin, dizziness, nausea and fever.
For example, zinc fumes can cause metal fume fever, a temporary illness similar to the flu. Chronic, long-term exposure to welding fumes can lead to siderosis (iron deposits in the lungs) and may affect pulmonary function.
Cadmium is a toxic metal which can be found on steel as a coating or in silver solder. Cadmium fumes can be fatal even with brief exposure, with symptoms much like those of metal fume fever. These two should not be confused. Twenty minutes of welding in the presence of cadmium can be enough to cause fatalities, with symptoms appearing within an hour and death five days later.
11.4.2 Gases
The gases that result from an arc welding process also present a potential hazard. Most of the shielding gases (argon, helium and carbon dioxide) are non-toxic. When released, however, these gases displace oxygen in the breathing air, causing dizziness, unconsciousness and death the longer the brain is denied oxygen.
Some degreasing compounds such as trichlorethylene and perchlorethylene can decompose from the heat and ultraviolet radiation to produce toxic gases.
Ozone and nitrogen oxides are produced when UV radiation hits the air. These gases cause headaches, chest pains, irritation of the eyes and itchiness in the nose and throat.
WIS1-40215
Arc Welding Safety 11-5 Copyright © TWI Ltd 2015
To reduce the risk of hazardous fumes and gases, keep the head out of the fume plume - a common cause of fume and gas overexposure because the concentration of fumes and gases is greatest in the plume.
In addition, use mechanical ventilation or local exhaust at the arc to direct the fume plume away from the face. If this is not sufficient, use fixed or moveable exhaust hoods to draw the fume from the general area. Finally, it may be necessary to wear an approved respiratory device if sufficient ventilation cannot be provided.
As a rule of thumb, if the air is visibly clear and the welder is comfortable, the ventilation is probably adequate.
To identify hazardous substances, first read the material safety data sheet for the consumable to see what fumes can be reasonably expected from use of the product.
Refer to the occupational exposure limit (OEL) as defined in the COSHH regulations which gives maximum concentrations to which a healthy adult can be exposed to any one substance.
Second, know the base metal and determine if a paint or coating would cause toxic fumes or gases.
Particular attention should also be paid to the dangers of asphyxiation when welding in confined spaces. Risk assessment, permits to work and gas testing are some of the necessary actions required to ensure the safety of all personnel.
11.5 Noise
Exposure to loud noise can permanently damage hearing and can also cause stress and increase blood pressure. Working in a noisy environment for long periods can contribute to tiredness, nervousness and irritability. If the noise exposure is greater than 85 decibels averaged over an 8 hour period then hearing protection must be worn and hearing tested annually.
Normal welding operations are not associated with noise level problems with two exceptions: Plasma arc welding and air carbon arc cutting. If either is to be performed then hearing protectors must be worn. The noise associated with welding is usually due to ancillary operations such as chipping, grinding and hammering. Hearing protection must be worn when carrying out or working in the vicinity of these operations.
WIS1-40215
Arc Welding Safety 11-6 Copyright © TWI Ltd 2015
11.6 Summary
The best way to manage the risks associated with welding is by implementing risk management programmes. Risk management requires the identification of hazards, assessment of the risks and implementation of suitable controls to reduce the risk to an acceptable level.
It is essential to evaluate and review a risk management programme.
Evaluation involves ensuring that control measures have eliminated or reduced the risks and review aims to check that the process is working effectively to identify hazards and manage risks.
It is likely that the Visual/Welding Inspector would be involved in managing the risks associated with welding as part of their duties.