Ventilation and Gas Interlock Systems

A fundamental requirement of BS 6173:2020 is that a kitchen's mechanical ventilation system must be electronically interlocked with the gas supply. This is a critical safety feature.

What it is: A system that physically prevents gas from flowing unless the ventilation fans are running. If a fan fails or is turned off, the gas supply is automatically and immediately shut down.
Why it's essential: Gas appliances produce toxic fumes, including carbon monoxide. The interlock eliminates the risk of these gases building up to dangerous levels in the kitchen.
What it covers: This rule applies to all mechanical extraction, including main canopies and separate extract fans for individual appliances like gas steamers.

Understanding Your Gas Safety Certificate (CP42)

"CP42" is the industry term for a Commercial Catering Gas Safety Certificate. It is the legal document proving a kitchen's gas installation has passed its annual safety inspection.

Legal & Insurance Requirements

An annual inspection by a Gas Safe registered engineer is mandatory under UK law. Failure to comply can result in prosecution, invalidated insurance, and the immediate closure of your kitchen facilities.

What’s Checked During the CP42 Inspection

All gas appliances (ovens, fryers, ranges, etc.).
Gas pipework integrity (leak testing).
The ventilation and gas interlock system to ensure it functions correctly as per BS 6173:2020.
Correct combustion and removal of fumes.

The Certificate Itself

The CP42 certificate is your official proof of compliance. It lists all tested equipment, its condition, and the engineer's Gas Safe registration details.

COMCAT Qualifications: Hiring a Competent Engineer

When you hire an engineer, they must hold the specific Commercial Catering (COMCAT) qualifications for your equipment. Ensure your chosen engineer is certified for all relevant categories.

COMCAT1: For core appliances like ranges, ovens, and boiling burners.

COMCAT3: For specialist equipment like deep-fat fryers and grills.

COMCAT5: A specific qualification required to test and service the catering ventilation and interlock systems.

Crucially, your engineer must hold all necessary qualifications to conduct a fully compliant inspection.

Actionable Steps for Your Facility

Schedule a Compliant Inspection: Contact a Gas Safe registered company and verify their engineers hold the required COMCAT 1, 3, and 5 qualifications.
Confirm Standards: Discuss your kitchen's compliance with the current BS 6173:2020 standard, particularly the interlock system.
Act on Failures Immediately: If the inspection reveals an 'At Risk' or 'Immediately Dangerous' fault, you must stop using the equipment and complete remedial work before it can be used again.
Keep Meticulous Records: File your CP42 certificates and maintenance logs securely. They are essential for any official inspection or insurance claim.