A respirator fit test is a safety procedure designed to ensure a tight-fitting mask creates an adequate seal against the wearer’s face, preventing the inhalation of hazardous airborne contaminants. A respirator only provides reliable protection when air cannot bypass the filter or cartridge through gaps around the seal. Since face shapes and respirator sizes are not standardized, a successful fit test confirms that a specific make, model, and size of respirator is effective for a particular user. This procedure validates the seal and measures potential leakage into the facepiece, and is mandatory before using a tight-fitting respirator in a contaminated atmosphere.
Essential Preparations Before Testing
Before the fit test begins, several mandatory steps must be completed to ensure the validity and accuracy of the results. The individual must first receive medical clearance, typically via a questionnaire reviewed by a licensed healthcare provider, to ensure they are physically capable of wearing a respirator. This confirms the user can safely handle the increased breathing resistance associated with mask use.
Proper selection of the respirator is required; the test must be performed with the exact make, model, and size the user intends to wear on the job. If the user wears other personal protective equipment, such as safety glasses or a face shield, those items must be worn during the fit test to ensure they do not interfere with the respirator’s seal. The test subject should also avoid eating, smoking, or chewing gum for at least 15 minutes before the test, as these activities can temporarily alter the sense of taste or smell.
The primary preparation is the requirement for a clean-shaven face where the respirator’s sealing surface contacts the skin. Facial hair, even minimal growth, prevents the formation of a seal and invalidates the test. Any hair between the face and the mask’s sealing surface creates channels for contaminants to leak around the edges. Regulatory bodies, such as the Occupational Safety and Health Administration (OSHA) in the US, mandate these preparations.
Step-by-Step Qualitative Fit Testing
Qualitative Fit Testing (QLFT) is a pass/fail procedure that relies on the wearer’s ability to detect a specific test agent through taste or smell. Common agents include saccharin (sweet taste) or Bitrex (bitter taste). The process begins with a sensitivity test, performed without the respirator, to confirm the subject can detect the test agent at a low concentration.
The subject dons a clear hood covering their head and shoulders. A diluted “threshold check” solution is nebulized into the hood; if the subject tastes the agent, the test proceeds. Once sensitivity is confirmed, the user puts on the respirator and performs a user seal check. The test administrator then nebulizes the stronger “fit test” solution into the hood at specific intervals to maintain a consistent concentration of the challenge agent.
With the challenge agent continuously present, the subject performs a series of standardized exercises, each lasting approximately one minute, to simulate typical workplace movements. The talking exercise often involves reading a specific passage, such as the “Rainbow Passage,” to ensure vocal cord movement and jaw articulation challenge the seal. These exercises include:
- Normal breathing.
- Deep breathing.
- Turning the head side-to-side.
- Moving the head up-and-down.
- Talking out loud.
- Bending over.
The purpose of these movements is to stress the respirator’s face seal, revealing leakage that might not be apparent while standing still. If the wearer does not taste or smell the test agent during the sequence of exercises, the test is passed for that specific respirator. If the agent is detected, the test is failed, and the user must be refitted with a different size or model before retesting.
Overview of Quantitative Fit Testing
Quantitative Fit Testing (QNFT) is an objective method that uses specialized equipment to numerically measure leakage into the respirator facepiece. Unlike the subjective, sensory-based pass/fail result of QLFT, QNFT provides a precise numerical value known as a “Fit Factor.” This factor is calculated by dividing the concentration of airborne particles outside the mask by the concentration measured inside.
Devices such as Condensation Nuclei Counters (CNC), like the PortaCount, or Controlled Negative Pressure (CNP) instruments are used for this testing. CNC devices sample ambient particles, while CNP devices create a temporary vacuum inside the mask to measure air leakage. The respirator used for QNFT must be modified with a small sampling probe extending into the breathing zone, allowing the instrument to take a continuous measurement.
The required minimum Fit Factor varies based on the type of respirator. Half-mask respirators typically require a Fit Factor of at least 100, while full-facepiece masks require a minimum factor of 500. A higher Fit Factor indicates a more effective seal and less leakage. QNFT is considered the more precise method and is often required for respirators used in higher-hazard environments or for full-facepiece masks.
When to Repeat the Fit Test
A respirator fit test is not a one-time event; it is a recurring procedure necessary to ensure continued protection. The most common regulatory requirement is that a tight-fitting respirator must be re-tested at least annually. This annual retesting ensures the user receives the expected level of protection, accounting for subtle changes in the face over time.
Beyond the annual mandate, an immediate retest must be conducted whenever a condition occurs that could affect the integrity of the mask’s seal. These conditions include significant changes in body weight, facial scarring, or dental changes such as the installation or removal of dentures. A retest is also necessary if the user switches to a different make, model, style, or size of respirator. If the user reports that the respirator no longer feels like it seals properly, an additional fit test is required before use.