Direct Answer: INDG479 is guidance rather than strict law, but it is widely recognized as the standard for demonstrating compliance with health and safety regulations for Breathing Apparatus (BA) fit testing. While not legally mandatory, UK Fire and Rescue Services are strongly advised to follow INDG479 protocols and use competent testers — such as those accredited through the Fit2Fit scheme — to support compliance and maintain high safety standards.

Table of Contents

• Understanding the Regulatory Shift
• Why Rigorous Fit Testing Matters for Firefighters
• Key Requirements of the INDG479 Guidance
• How PortaCount™ Technology Supports INDG479 Compliance
• Integrating Data into Your Safety Protocols
• Moving Forward with Confidence

Understanding the Regulatory Shift

UK Fire and Rescue Services (FRS) have long relied on the "DCOL" process, which allowed certain exemptions from fit testing practices set out in other industries. This changed as of January 1, 2026, when the Health and Safety Executive (HSE) formally withdrew this exception.

It is important to clarify that HSE Guidance Note INDG479 (revised October 2025) is guidance, not strict law. However, INDG479 is widely regarded as the practical standard for demonstrating compliance with the Control of Substances Hazardous to Health Regulations 2002 (COSHH). Inspectors may use adherence to INDG479 to assess whether employers are meeting their legal health and safety duties.

Adhering to INDG479 is strongly advised for the following reasons:

• Legal Standing: INDG479 does not carry the force of law, but it serves as an authoritative reference. Regulators often refer to its recommendations when evaluating compliance with COSHH.

• Competence: While not compulsory, using a fit tester accredited through a recognized scheme, such as Fit2Fit, helps demonstrate the necessary competence expected for legal compliance and good practice.

• Applicability: Fit testing remains required for all tight-fitting facepieces, including the positive pressure masks commonly used by firefighters.

• Updates: The October 2025 revision of INDG479 specifically addresses updated protocols for face fit testing in high-risk environments, ensuring guidance reflects current best practices.

For breathing apparatus, FRS must be able to demonstrate they are following established safe standards. Consistent alignment with INDG479 supports both compliance and liability management, providing clarity and assurance to those responsible for worker safety.

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Why Rigorous Fit Testing Matters for Firefighters

Firefighters routinely enter Immediately Dangerous to Life or Health (IDLH) environments, where exposure to toxic gases, smoke, and oxygen-deficient atmospheres is a constant threat. In these conditions, the fit of a BA facepiece is a critical last line of defense. An inadequate fit can lead to failure, as HSE studies have shown that even positive pressure respirators require fit testing. Under certain conditions, when air demand exceeds supply, the respirator can momentarily switch to a negative pressure mode, increasing the risk of leakage.¹ 

Quantitative fit testing provides an objective, numerical measurement of a respirator’s fit, known as a Fit Factor. This data-driven method is essential for testing BA facepieces, as qualitative tests that rely on a user's sense of taste or smell are not adequate for this purpose.

For firefighters, a quantitative pass result offers a high degree of confidence that their specific make and model of BA facepiece can provide the necessary level of respiratory assistance when correctly donned. It confirms the equipment is right for the individual, which is fundamental to occupational safety.

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Key Requirements of the INDG479 Guidance

Adherence to INDG479 is now central to BA fit testing programs for all Fire and Rescue Services. This guidance sets a clear framework for validating the fit of any tight-fitting respirator.

Quantitative Fit Testing (QNFT) is Mandatory

INDG479 specifies that for full-face respirators, such as those used with BA, Quantitative Fit Testing (QNFT) is the required method. This involves using an instrument to measure the precise amount of leakage into the respirator while the user performs a series of prescribed exercises that simulate movement on the job.

The Role of Competent Fit Testers

The guidance places significant emphasis on the competence of the individual conducting the fit test. A competent tester must have a thorough understanding of the testing equipment, the specific exercises, and the ability to identify a poor fit. They must also know how to coach a wearer to achieve a proper fit and when to recognize that a different size or model of respirator is needed.

Robust and Accessible Record-Keeping

Under COSHH and INDG479, maintaining detailed records is not optional. Fit test records must include the date of the test, the individual’s name, the specific make, model, and size of the respirator, and the quantitative Fit Factor achieved. These records are vital for demonstrating compliance during audits and for managing the ongoing respiratory health of personnel.

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How PortaCount Technology Supports INDG479 Compliance

As Fire and Rescue Services adapt to these updated requirements, using the right instrumentation is key to building an efficient and reliable compliance program. The PortaCount™ Respirator Fit Tester is a widely adopted solution for QNFT, offering distinct benefits that align directly with the needs of the FRS.

Unmatched Quantitative Accuracy

The PortaCount™ Fit Tester provides precise, objective data on respirator fit. It uses advanced measurement technology to calculate a Fit Factor, giving a clear pass or fail result based on the standards set within INDG479. This level of accuracy is essential for validating the performance of BA used in high-risk scenarios.

Simplified and Reliable Operation

Designed for use in demanding environments, the PortaCount™ instrument is robust and user-friendly. Its real-time FitCheck™ Mode offers immediate visual feedback on the respirator’s fit during the donning process. This feature enables trainers to quickly guide firefighters on how to adjust their respirator for a better fit before the official test even begins, helping to improve pass rates and build wearer confidence.

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Integrating Data into Your Safety Protocols

Compliance with INDG479 extends beyond the test itself; it requires seamless data management. Modern fit testing solutions can help streamline this process.

Automated Reporting and Data Management

The PortaCount™ Fit Tester integrates with TSI Link™ Solutions, a cloud-based software platform that automates data logging and report generation. Test results from multiple stations or fit testers can be synchronized to a central database, creating a single source of truth for all compliance records. This capability significantly reduces the administrative burden on safety officers and helps simplify audit preparation. The instrument's calendar function also enables automated email reminders for fit tests, allowing staff to book their own appointments.

Enhancing Training and Safety Culture

Using the data from quantitative fit tests can enhance training. By showing firefighters their own Fit Factor results, trainers can reinforce the importance of proper donning procedures. This transparency helps foster a strong safety culture where every individual takes ownership of their personal protective equipment.

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Moving Forward with Confidence

The withdrawal of the DCOL process represents a positive step forward in modernizing safety standards for the UK Fire and Rescue Service. By fully embracing INDG479 and implementing rigorous quantitative fit testing programs, the FRS can operate with a higher degree of confidence in the respiratory equipment provided to its personnel.

The deadline has passed, and these standards are now in effect. It is the responsibility of every service to ensure its protocols, equipment, and training are fully aligned with this new benchmark for firefighter safety. Investing in accurate, reliable, and efficient fit testing is a direct investment in the health and well-being of those who serve on the front lines.

Ready To Take the Next Step?

• Learn more about the PortaCount™ Respirator Fit Tester: Explore how advanced quantitative fit testing technology supports compliance and safety for Fire and Rescue Services. Discover PortaCount™

• Speak with an expert: Get personalized guidance on implementing effective fit testing programs for your team. Contact our specialists

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¹ https://www.fit2fit.org/wp-content/uploads/2019/04/Guidance-on-RPE-Fit-testing.pdf