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Breathe Easy

Published: 10th Apr 2009

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Respiratory Protective Equipment (RPE) has been placed fi rmly at the bottom of the hierarchy of control and is often referred to as a control measure of last resort. The Control of Substances Hazardous to Health (COSHH) Regulations have enshrined the hierarchy in legislation for over 20 years. This hierarchy indicates the relative desirability and effi cacy of various forms of control. (See fi gure 1).

There are a number of reasons why RPE sits at the bottom of this league table; these include:

  • The efficacy of RPE varies significantly in the workplace and is greatly reduced by factors such as poor fitting, lack of training and interaction with other PPE
  • The use of RPE places a heavy reliance on the skills and training of the employee
  • RPE can interfere with and be influenced by other control measures
  • RPE interferes with, and can be influenced by, the work undertaken by the employee
  • In many cases there is no way of telling if the RPE is failing as a control measure

Despite the fact that RPE is listed as a last resort there are a number of scenarios where it can be used as an effective control measure, such as:

  • Where an inhalation exposure risk remains after you have put in place other reasonable controls
  • Short term or infrequent exposures where other control measures are not considered to be reasonably practicable
  • As a short term measure whilst you are introducing other controls
  • As a means of escape in the event of an emergency
  • Undertaking emergency work where other means of control are not reasonably practicable

Types of RPE

The range of RPE available is vast but at the most basic level there are only two main categories of RPE, Breathing Apparatus (BA) and Respirators.

Breathing Apparatus is RPE which is supplied with breathable quality air from one of three sources:

  • bottles carried by the users - Self Contained Breathing Apparatus [SCBA], commonly seen in use by the Fire & Rescue Services
  • A compressed airline supply
  • Fresh air - drawn or forced through a hose with the end located in clean, uncontaminated air

Respirators take the workplace air and filter it to a suitable standard for breathing. Respirators are generally classified as being powered or negative pressure in design. Figure 2 illustrates the basic types of RPEquipment available. It is possible to further categorise RPE and a useful guide providing more detail including relevant European Standards is the Health and Safety Executive (HSE)’s “Respiratory Protective Equipment at Work: A Practical Guide” (see references at the end).

Breathing apparatus

Self-Contained Breathing Apparatus (SCBA) is usually used in emergency or situations where oxygen depletion or other ‘Immediately Dangerous to Life or Health’ (IDLH) environments might exist or arise, such as spillage response or confined space activities. SCBA use is restricted by the limited duration of the air supply (usually only 30 minutes). The weight of the cylinders being carried also limits mobility and imposes a high workload on a user.

A wide range of facepieces are available for airline BA (only some of which are suitable in oxygen deficient or IDLH environments), from demand valve facepieces which offer the optimal protection, full and half-masks, full suits (airsuits), half-suits and hoods, to visors often seen in paint spraying operations.

Fresh Air Hose BA uses a broader bore hose to draw air either unassisted, or assisted with a fan or blower. Securing the inlet of the air hose in an area which is and will remain uncontaminated is obviously essential for the safety of the user. Again different headpieces are available.

One of the main reasons for selecting BA over Respirators is the higher Assigned Protection Factors (APF) afforded by the former. (APF is the ratio of concentration of contaminant in workplace air divided by concentration of contaminant breathed in). Whilst quoted APFs vary considerably depending on which country’s standards are considered, using UK’s recommended APFs, respirators can only provide an APF of up to 40, whilst full facepiece, demand valve BA can offer up to 2000. It is important to recognise that these very high APFs will only be achieved in a workplace with an equally good overall RPE programme, and the effort needed to achieve should not be underestimated.

Respirators

A respirator takes workplace air and filters it prior to the user breathing the air. It is common to categorise types of respirators according to whether they are powered or filtering. It is also common to differentiate filtering respirators according to whether they are used for protection against particulates or against gases and vapours, though some filtering respirators will do both.

Powered helmets or hoods are available with filters and batteries commonly mounted on waist belts, though some suppliers avoid trailing hoses and batteries by fitting these within the helmet unit itself. As well as offering respiratory protection some also offer, skin, head and eye protection depending on the design of the headpiece. Incorporating other PPE can make these units desirable as it can avoid the difficulties sometimes seen in using tight fitting respirators with multiple items of other PPE.

Tight fitting filtering respirators are negative pressure respirators and rely on achieving a good face seal to obtain the stated APF. Since adequate performance can only be achieved if the respirator fits the user, individual face fit testing is a necessary part of any RPE programme using tight fitting respirators. (See the later section on fit-testing.) These span the range through disposable dust masks to half and full facepieces with gas and vapour protection. For half masks, filters may be integral so that there are no serviceable parts and the whole facepiece with filters is disposed of (reducing maintenance and record keeping requirements). Alternatively facepieces can take replaceable filters. Correct filter choice is essential for gases and solvents as different media only remove particular contaminants, so great care is required both in correct selection and on-going use.

Selection of RPE

Selection of RPE is inextricably linked to the health and safety management system of a facility and in particular the chemical hazards management and risk assessment system. Even to reach the decision that RPE is needed involves progressing through many stages of the process; the materials and their hazards must be identified, tasks defined, existing controls evaluated and exposures assessed before even starting to decide which RPE is the best for the task in question.

Only RPE that is ‘approved’ may be used. Within the EU RPE must satisfy the Basic Health and Safety Requirements of the PPE Directive and carry the appropriate ‘CE’ mark. Not only must it be approved but it must also be ‘adequate’, i.e. able to achieve at least the required level of protection, and ‘suitable’, i.e. able to provide that protection when considering the task, the wearer and the working environment.

The various factors to consider when selecting RPE can be grouped into three broad areas: Contaminant Related, Task Related and Wearer Related.

Contaminant related

The first stage in selecting RPE is determining if there is the potential for oxygen deficient or other IDLH atmospheres. If this potential exists then only BA can be used and a detailed assessment of the operations, including consideration of provision of escape air needs to be conducted. Where oxygen deficient or other IDLH situations do not exist the next factors to consider revolve around the contaminants present:

  • All the contaminants that may be present in a concentration liable to exceed the exposure limit either individually or additively (or even synergistically) need to be identified
  • The physical state - whether a dust (or other aerosol), gas, vapour or fume - must be established
  • Ideally, the concentration of the contaminants present during the activity should be measured (this links back to the exposure monitoring and risk assessment programme) or if not possible, likely concentrations estimated; both dustiness and volatility impact this
  • Material hazards need to be assessed, consideration must be given to whether eye or skin irritation or skin sensitisation may occur on exposure, and it must be determined if the material has adequate warning properties (taste/smell) to alert the user to a poorly fitting respirator or fully loaded filters

Task related

Several task related factors need to be considered beyond those already mentioned regarding oxygen depreciation, IDLH and escape:

  • Duration of use and work-rate; tight fitting masks should generally not be worn for more than one hour hour for comfort factors
  • Temperature and humidity, not only because of comfort and heat stress, but high humidity can also adversely affect capacity of solvent filters
  • Vision, communication
  • Mobility and workplace restrictions; the more congested a workplace and mobile the operator has to be the less heavy and restrictive (e.g. through trailing hoses) the RPE needs to be

Wearer related

Individual factors are important in RPE selection, the most obvious being facial size and shape, and facial hair and use of glasses, all of which can interfere with the face seal. The medical fitness of an employee also needs to be considered, particularly for those with respiratory disorders. General fitness will also need to be considered for physically demanding use of SCBA. Lastly, as hinted at earlier, the requirement for either the RPE to provide skin, eye or head protection, or if the RPE interferes with this and other PPE being worn must also be accounted for.

Other considerations

Whilst protection of staff rather than cost is the priority of an RPE programme, costs and indeed the effort needed to run a successful programme are real life considerations. Costs of an RPE programme can be vastly underrated, usually taking into account only the costs of the RPE itself. A truer picture can be gained by building in costs of spares, training time, and time for cleaning and maintenance etc. In reality RPE programme costs can be many times greater than just the cost of the RPE and this should be considered when deciding on whether it is truly not reasonably practicable to engineer out the exposure.

It has earlier been emphasised how RPE must sit within the health and safety management system, especially the chemical management system, rather than being separate to these systems. Some of the aspects of managing RPE may be specialist, but key elements supporting RPE usage such as staff fitness, training and supervision for example, are common with other parts of the overall programmes of a facility.

Staff training must be carried out before using RPE. Classroom, video, or on-line training may all be appropriate but training should always include a practical element even for simple dust masks when the user can practice correctly fitting a mask. How important this aspect is will be discovered during fit-testing. Of course for complex RPE, such as BA used in life-threatening situations, the training must be carried out to the highest standards and regularly refreshed to ensure users are always fully competent.

Having short-listed RPE that has the necessary APF to adequately reduce exposures, all operators and management should be involved in the final selection to ensure a full understanding and agreement by all parties about the decision.

The maintenance strategy must be considered - in essence, whether users will be trained to maintain the RPE or whether it will be centrally maintained either by in-house staff, or a contractor. In any case those maintaining RPE must be competent to do so and appropriate training must be given. If using BA, the maintenance regime will need to include the breathing air compressors and periodic checks on the cleanliness of the breathing air supply. Some air purifiers do have continuous monitoring systems which will also need to be maintained.

A proper RPE programme will also include proper supervision, audit and review. It is easy and common place for poor practices to creep into RPE use, and so the part that proper supervision plays in maintaining any RPE programme should not be ignored. An RPE programme that does not incorporate proper supervision will not operate optimally. In addition, periodic, formal audit of the system elements and review of the programme based on the findings of the audits is an important aspect of the overall programme, identifying deficiencies and opportunities for continuous improvement.

Fit testing

In the past, research has shown that the actual protection afforded by RPE is not as good as was originally thought. Tests undertaken under workplace conditions revealed that the respirators did not perform as well as they did in the laboratory and that in some instances they afforded little or no protection.

There are a number of reasons for this apparent failure of RPE including improper wearing of the respirator or ineffective training. However in a significant number of cases it was found that the respirator simply didn’t fit the employee. The performance of tight-fitting facepieces relies on achieving a good contact between the wearer’s skin and the face seal of the respirator.

As all our clothes and much PPE comes in different sizes it is unlikely that one particular type or size of RPE facepiece will fit everyone. Inadequate fit will significantly reduce the protection provided to the wearer. Any small gap in the seal between the facepiece and the face will allow contaminant ladened air to enter inside the mask and be breathed in.

In order to ensure that this does not occur all employees need to go through fit testing for any tight fitting facepiece that they wear. If an employee wears more than one type of tight fitting facepiece then each type of facepiece should be subjected to fit testing.

A fit test should be carried out when initial facepiece selection takes place and where an untested facepiece is already used. Retesting will also be required if a new facepiece is selected or if the employees face changes e.g. through weight loss/gain or dental work. Fit testing is only required for tight fitting facepieces and as such is not required for devices such as compressed air line fed or powered respirators which rely on a positive pressure inside the mask.

There are two basic types of RPE fit testing - qualitative and quantitative.

Qualitative fit testing is a simple pass/fail test based on the wearer’s subjective assessment of the leakage, via the face seal region, of a test agent which has a particular taste or odour. These tests are relatively simple to perform and are suitable for half masks and filtering facepieces.

Quantitative fit testing provides a numerical measure of the fit, known asthe fit factor and is recommended for full-face masks. These tests give an objective measure of face fit. They require specialized equipment which measures the concentration of an agent both inside and outside the facepiece and are more complicated to carry out than qualitative methods.

A fit test report should be issued which will normally indicate whether the employee has passed or failed the test and in some instances the fit factor which has been achieved. The fit factor is a measure of how well a particular facepiece seals against the wearer’s face. A higher fit factor number means the facepiece achieved a good contact between the face seal and the face during the test. It is important not to confuse the fit factor with the ASP (Assigned Protection Factor) mentioned earlier.

Fit testing should only be undertaken by a competent person, who has adequate knowledge, and has received adequate instruction and training in the selection, examination and fitting of RPE as well as in the appropriate testing techniques. There are a number of companies, including RPE manufacturers, who carry out fit testing as a service. The HSE is currently supporting the pilot of an industry self regulating accreditation scheme for fit testers known as fit2fit.

Summary

The use of RPE can and does act as an effective control measure in reducing exposures to hazardous substances. However, the level of protection provided can be greatly reduced unless a proper selection and use process is followed.

It is essential that when RPE is used it is integrated with other control measures such as; engineering controls, other PPE and information, instruction and training. Without this integration then the RPE is unlikely to provide the level of control required.

References:

Respiratory Protective Equipment at Work: A Practical Guide. Health and Safety Executive. HSG53. ISBN 0-7176-2904-X

Fit testing of Respiratory Protective Equipment (facepieces); Health and Safety Executive Information Document HSE 282/28

Effectiveness of RPE during asbestos removal work. HSE CRR No. 112/1996 Howie RM, et al.

BOHS Directory of Occupational Hygiene Consultants. Download on-line version, http://www.bohs.org/indexTemplate.aspx/Home/Professional/Consultants or request a hard copy by phone from the BOHS office, +44 (0)1332 298101.

Published: 10th Apr 2009 in Health and Safety International

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