Assigned Protection Factors (APF) Explained: How Businesses Choose the Right Respirator
Understanding respirator protection levels for silica, asbestos and other workplace hazards
Selecting the correct respiratory protective equipment (RPE) is an important part of protecting workers who may be exposed to airborne hazards.
A disposable mask or respirator should not be selected simply because it is commonly used or readily available. The correct respirator depends on the workplace hazard, the level of exposure and the amount of protection required.
One of the key factors used when selecting respiratory protection is the Assigned Protection Factor (APF).
Understanding APF helps businesses determine what type of respirator may be suitable for workers exposed to silica dust, asbestos fibres, hazardous dusts, fumes, vapours and other airborne contaminants.
What Is an Assigned Protection Factor (APF)?
An Assigned Protection Factor (APF) is a rating that indicates the level of respiratory protection a respirator is expected to provide when it is correctly selected, fitted, maintained and used as part of a respiratory protection program.
Put simply:
The APF indicates how much a respirator can reduce a worker’s exposure to an airborne contaminant when used correctly.
For example:
A respirator with an APF of 10 means the concentration of the airborne contaminant inside the respirator is expected to be reduced to approximately one-tenth of the concentration outside the respirator.
A higher APF provides a higher level of expected protection.
Why Is APF Important When Selecting Respiratory Protection?
Businesses must select respiratory protection based on the risk associated with the work being performed.
The correct respirator is determined by considering:
The type of airborne hazard
The concentration of the contaminant
The workplace exposure standard
The duration of exposure
The task being performed
The level of protection required
The aim is to ensure the selected respirator provides enough protection for the specific workplace environment.
How Do Businesses Determine What Respirator Is Required?
Respirator selection should begin with understanding the hazard.
A workplace should consider:
1. What airborne contaminant is present?
Examples include:
Hazardous dusts
Respirable crystalline silica
Asbestos fibres
Coal dust
Mineral dusts
Fumes
Welding fumes
Metal fumes
Combustion by-products
Vapours and gases
Solvent vapours
Chemical vapours
Industrial gases
Different contaminants require different approaches to control and different respiratory protection solutions.
2. What Level of Exposure Exists?
The required respiratory protection depends on the concentration of the airborne hazard.
For example, a worker performing occasional low-risk tasks may have different respiratory protection requirements compared with a worker regularly exposed to high concentrations of airborne contaminants.
Exposure monitoring, workplace assessments and risk assessments help businesses determine the level of protection required.
Understanding Workplace Exposure Limits (WEL) and Workplace Exposure Standards (WES)
Before selecting respiratory protective equipment (RPE), businesses must understand the level of airborne contamination present in the workplace.
A Workplace Exposure Limit (WEL) is a term commonly used internationally to describe the maximum concentration of an airborne contaminant that a worker should not be exposed to over a defined period.
In Australia, this is generally referred to as a Workplace Exposure Standard (WES).
A WES represents the airborne concentration of a substance that must not be exceeded over a specified averaging period, usually expressed as an 8-hour time weighted average (TWA).
Workplace exposure limits/standards are used when assessing:
The level of airborne contamination present
Whether existing controls are effective
Whether additional controls are required
The required level of respiratory protection
How Do Exposure Limits Determine the Required Respirator?
The exposure level measured in the workplace helps determine the required Assigned Protection Factor (APF).
The calculation is:
Required APF = Workplace airborne concentration ÷ Workplace Exposure Standard
For example:
A worker is exposed to a contaminant concentration of:
1 mg/m³
The workplace exposure standard is:
0.05 mg/m³
Calculation:
1 ÷ 0.05 = 20
This means respiratory protection with an APF of at least 20 would be required.
The respirator selected must provide adequate protection for the exposure level while also considering:
The type of contaminant
The task being performed
Exposure duration
Respirator limitations
Worker fit testing requirements
Example: Respirable Crystalline Silica (RCS)
Respirable crystalline silica is generated during activities including:
Engineered stone fabrication
Concrete cutting
Grinding
Drilling
Mining
Quarrying
Demolition
The Australian workplace exposure standard for respirable crystalline silica (RCS) is:
0.05 mg/m³ as an 8-hour time weighted average (TWA).
This means worker exposure must not exceed this concentration averaged over an 8-hour working day.
Example:
Measured silica exposure:
0.5 mg/m³
Exposure standard:
0.05 mg/m³
Required APF:
0.5 ÷ 0.05 = 10
A respirator with an APF of at least 10 may therefore be required, subject to the workplace risk assessment, respirator selection and fit testing.
Example: Asbestos Exposure
Asbestos exposure involves inhalation of airborne asbestos fibres released during activities such as:
Asbestos removal
Demolition
Building refurbishment
Maintenance work involving asbestos-containing materials
The workplace exposure standard for asbestos is:
0.1 fibres/mL of air averaged over an 8-hour period.
Respirator selection for asbestos work must consider:
The type of asbestos activity
Potential fibre release
Exposure monitoring results
Required APF
The respiratory protection equipment selected
Higher-risk asbestos activities may require respiratory protection with a higher APF to maintain worker exposure below the applicable exposure limit.
Other Hazardous Dusts, Fumes and Vapours
Respiratory protection may also be required for workers exposed to:
Welding fumes
Metal dust
Chemical vapours
Manufacturing emissions
Pharmaceutical particles
Industrial contaminants
The correct respirator depends on the contaminant and the required level of protection.
Examples of Different Respirator Protection Levels
Respirator Type APF
P2/N95 10
Half face 10
Full Face with P2 filters 50
Full Face with P3 filters 100
Why Respirator Fit Testing Is Critical
Choosing a respirator with the appropriate APF is only one part of respiratory protection.
For tight-fitting respirators, the equipment must also create a proper seal against the worker’s face.
A respirator that does not fit correctly may not provide the expected level of protection.
This is why respirator fit testing is an important part of workplace respiratory protection programs.
A P2 mask fit test or respirator fit test helps confirm that the selected respirator model and size are suitable for the individual worker.
APF, Fit Testing and Worker Health Monitoring Work Together
Managing airborne hazards requires more than selecting a respirator.
A comprehensive workplace respiratory protection program may include:
Hazard identification
Exposure monitoring
Respirator selection
Respirator fit testing
Worker training
Equipment maintenance
Silica Health Monitoring
Asbestos medicals
Respiratory health assessments
Each element supports the overall goal of reducing worker exposure to hazardous airborne contaminants.
Respirator Selection Is About Matching Protection to Risk
There is no single respirator suitable for every workplace.
The correct respiratory protection depends on:
The airborne hazard
The exposure level
The required protection factor
The selected equipment
The worker’s ability to use the equipment correctly
Understanding Assigned Protection Factors helps businesses make informed decisions when protecting workers from silica, asbestos and other hazardous airborne substances.
