Selection And Maintenance Of Respiratory Protective Equipment

Selection Method

1) Determining the Nature and Severity of Hazardous Environments

Occupational Health Standards
The national standard (GB) and European standard (EN) define the Occupational Exposure Limit (OEL), while the U.S. OSHA standard specifies the Permissible Exposure Limit (PEL), and the U.S. NIOSH standard defines the Recommended Exposure Limit (REL). These three limits serve the same purpose: if the concentration of airborne pollutants is below the OEL, PEL, or REL, workers can be repeatedly exposed over a long period without experiencing harmful effects. However, if the concentration exceeds these limits, it may cause varying degrees of harm to the human body.

The Chinese national standard GB/T 18664-2002, referencing the NIOSH Pocket Guide to Chemical Hazards and EN 529-2005, also defines the Immediately Dangerous to Life and Health (IDLH) concentration. When airborne pollutant concentrations exceed the IDLH value, exposure can be fatal, cause permanent health damage, or impair a person’s ability to escape.

IDLH and non-IDLH environments are classified based on GB, EN, and U.S. standards. An environment is considered IDLH if it meets any of the following conditions:

1. Oxygen deficiency (as per the Chinese standard, oxygen concentration below 19.5%) or uncertainty about oxygen levels.
2. Unknown nature or composition of airborne pollutants.
3. Presence of one or more airborne pollutants exceeding IDLH levels or when concentrations are unknown.

A non-IDLH environment is one where all airborne pollutants are known, their concentrations are determined, and they exceed the OEL, PEL, or REL but remain below IDLH levels.

2) Selecting Protective Equipment Based on the Hazardous Environment

1. For IDLH environments, supplied-air respiratory protection must be used, such as a positive-pressure self-contained breathing apparatus (SCBA) or an airline system with an auxiliary escape device, ensuring complete isolation from harmful air.
2. For non-IDLH environments, choose filtering or higher-level protective equipment.
3. For environments where pollutant concentrations are below OEL, PEL, and REL, lower-grade protection or no protection may be sufficient.
4. If airborne pollutants pose a risk to the eyes or face (e.g., irritation or corrosion), a full-face respirator or a ventilated hood should be used.

3) Selection of Respiratory Protection in Non-IDLH Environments

1. Calculate the Hazard Factor (HF) by determining the ratio of airborne pollutant concentration in the workplace to the corresponding OEL, PEL, or REL.
2. Each type of respiratory protective equipment has an Assigned Protection Factor (APF) specified in national standards. The selected equipment should have an APF greater than the HF.
3. If multiple airborne pollutants are present, calculate the HF for each and use the highest value for selection.
4. When correctly worn, the expected exposure concentration for the user is the ambient hazardous concentration divided by the APF of the selected respirator.

4) Selection of Filtering Elements When Filtering Respiratory Protection is Applicable

1. For particulate pollutants, use filtering pads or dust masks. Particulates are classified as oil-based or non-oil-based.
2. For toxic gases and vapors, select appropriate cartridges (filters) according to strict standards or consult safety professionals.
3. For environments with both toxic particulates and gases/vapors, choose multi-functional combination cartridges based on pollutant types.

5) Replacement of Filtering Elements

The service life of filtering elements depends on factors such as pollutant type and concentration, breathing rate, work intensity, environmental temperature, and humidity. Consult safety professionals when in doubt.

General guidelines for determining filter replacement time:

1. If the user experiences increased breathing resistance or detects an odor/irritation, replace the filter immediately. For pollutants with poor or no warning properties (e.g., those with odor thresholds much higher than occupational limits), use respirators with end-of-service-life indicators (ESLI) or supplied-air respirators.
2. For routine operations, establish a replacement schedule based on experience, experimental data, or other objective methods.
3. Record usage time after each session to help determine replacement timing.
4. Filters for low-boiling organic compounds (<65°C) degrade faster and should be replaced after each use.
5. For other organic compounds, if there is a long gap (days or weeks) between uses, consider replacing the filter before reuse.