Understanding respirator PPE

The subject of Respirator Personal Protective Equipment is confusing until one understands the basic concept requirements.

OHS Act defines Respiratory Protective Equipment as a device which is worn over at least the mouth and nose to prevent the inhalation of air borne hazardous chemical substances and which is of a type or conforms to a standard approved (normally an international or SABS Code) by the Minister of Employment & Labour.

A respirator zone means an area where the concentration of an airborne hazardous chemical substance exceeds the recommended OEL limits for that substance. Such zones are normally identified with respirator symbolic signs.

The Occupational Health and Safety Act 85 of 1993 (OHS Act) details the recommended Time Weighted Average Occupational Exposure Limits (OEL) for recognised hazardous chemical substances. Suitable testing for chemical substances concentrations would be necessary to establish actual contaminant levels. It is an OHS Act offence for Employers who expose their Employees to OEL levels above the recommended OEL values

What precautions are available?
OHS Act requires the Employer to assess the potential hazards and threats a workplace or the work activities performed can have on the health and safety of the employees. The risks are to be eliminated or mitigated where possible & precaution applied where risks still exist. Based on the findings of the assessments a risk mitigation process should be followed as outlined below.

There is a basic risk reduction process of eliminate, separate and protect that should be applied to reduce the risk exposure:

Firstly, elimination by the employer considering what can be done to reduce the respirable risk as the source of the risk. (e.g. a water spray could be used to dampen down and reduce dust generated along a gravel road with airborne dust producing vehicles traveling along the road or even better tar the road). Often improving ventilation, such that the airflows are away from the worker, can reduce or eliminate the particulates or vapour gas risk so that the respiratory protection requirement is unnecessary. Elimination is often done through applying engineering controls, like:

• Changes in the work process that reduce or eliminate worker exposure.
• Substitute less hazardous chemicals or products for the more hazardous materials.
• Provide enclosures that prevent direct exposure (by separation) and/or
• Use ventilation to dilute or remove the contaminant.

Secondly, separation by enclosing or isolating the work process from the affected workers or by increasing the distance between the dust generating source and the employee to reduce the risk (e.g. the vehicle driver’s exposure to dust while travelling alone the gravel road will be reduced if a closed driver cab was provided on the vehicle. In some cases, operators could work from air-conditioned enclosed booths to avoid inhaling production area respiratory exposure risks.

Thirdly, the last resort is to provide personal protection, by providing respiratory PPE to employees to reduce the employee’s exposure to the risk as no other practical method of protection is possible.

Respiratory Protection
The basic purpose of any respirator is to protect the respiratory system from the inhalation of hazardous materials, substances, gasses, poisons, toxins, etc., from the atmosphere. Because of the diverse types of respiratory risks, i.e. low oxygen, hazardous atmospheres, dusts, fumes, mists, gasses, vapours, combination and special case risk types, there is no single method of respiratory protection, which can provide adequate respirable protection for all these risks.

Furthermore, the protection could be required on a one-off/single-use basis (e.g. sandpapering a table), where a dusk mask could be used or required on an ongoing repeated or continuous exposure risk hazard basis (e.g. regular chemical dosing cycles or continuous spray painting in a spray booth).

The work activity and work duration will determine the respirator type and capacity necessary to provide a suitable level of respiratory protection for the task being performed. The level of respirator protection may require that a filter-paper mask to a half- or full-face piece mask to be used, with a single or double filter cartridge fitted or with an air-supply line feed.

Respirator Types
There are two main concept category types of respirator protection available are shown in the Respirator Types selection flow-table and it illustrates the respirator protection category differences & the various respirator types within these two respirator categories.

The Air-Purifying Respirator Cartridges or Canisters have a similar basic design, which may be designed using layers of filtering materials to filter out the particulates only or designed with different chemical reagents or catalysts to absorb or react with various concentrations of different vapour and gas contaminants thereby removing them from the air being breathed. Then there is the respirator designed to filter out both particulates & the specific chemical vapours & gasses contaminating the air, by a specifically selected dual purpose respirator to remove the particulates & the chemical contaminates from the air breathed. A cartridge vapour gas removal filter provides protection against contaminant concentrations of 10ppm to 1000ppm by volume, depending upon the chemical contaminant involved, and where ppm means parts per million. This protection capacity value must be checked against the filter’s packaging instructions.

The Atmosphere Supplying Respirators are always used where there is a life-threatening atmosphere situation present involving an oxygen deficient atmosphere, poisonous, corrosive or toxin gasses or similar risks are present or if it is uncertain if the atmosphere is safe to breathe. Here two supply processes need to be considered where the surrounding atmosphere is life threatening hazardous:

Firstly, the Airline or Air-hose type respirator, where the air supply is drawn or pumped from a safe air breathing atmosphere area through a hose or pipeline to normally a full face-piece type mask. (e.g. the air supply to a person working in a confined space of a tank with the air supplied by a fresh air hose/ pipe drawing air from the safe atmosphere outside the tank’s confined space, or an air blower pumped, or an oil and air filter cleaned, pressure reduced compressed air breathing air supply).

Secondly, the Breathing Apparatus type respirators, where the air supply could be from a closed-circuit air re-breather system worn on the chest, with a carbon dioxide removal and oxygen generation chemical reagent or a small oxygen cylinder (i.e. a mine’s proto team rescue breathing pack) or from an open circuit self-contained breathing apparatus (SCBA) with air supply cylinder(s) carried on the users back (e.g. like the firemen wear at fires). SCUBA is the underwater diver BA version. 

This series, by SHE and Risk Management Consultant Leighton Bennett of Benrisk Consulting, is written with occupational health and safety officers in mind. He can be contacted at +27 (0)83 325 4182, benrisk@mweb.co.za.