A gas safety inspection is a systematic check of all gas appliances and installations in your property, carried out by a Gas Safe registered engineer. For landlords, it's a legal requirement; for homeowners, it's essential for safety and peace of mind.
When is your gas safety inspection?
Let's check your preparation status.
What is a gas safety inspection?
A gas safety inspection is a comprehensive check of your gas appliances and installations to ensure they're safe to use and meet legal standards.
The inspection covers:
- All gas appliances (boilers, fires, cookers, heaters)
- Gas pipework and connections
- Flues and ventilation
- Safety devices and controls
- Gas meter and emergency controls
Who needs inspections:
- Landlords - legally required annually
- Homeowners - strongly recommended annually
- Businesses - required under Health and Safety at Work Act
- Housing associations - mandatory for all social housing
A gas safety inspection focuses on safety, not performance. The engineer checks whether appliances are dangerous, not whether they're working efficiently. For performance and efficiency checks, you need a separate service (though many engineers offer combined packages).
Before the inspection: How to prepare
Proper preparation ensures the inspection goes smoothly and is completed in a single visit.
1-2 weeks before
Book the inspection:
- Contact a Gas Safe registered engineer
- Verify their registration online (GasSafeRegister.co.uk)
- Confirm they're qualified for your appliance types
- Get written confirmation of date, time, and cost
For landlords:
- Notify tenants in writing (24-48 hours' notice minimum)
- Explain why access is needed
- Confirm someone will be present
- Provide tenant with engineer's details
For homeowners:
- Schedule when you'll be home
- Allow 30-90 minutes depending on property size
- Book time off work if necessary
1-3 days before
Prepare the property:
- Clear access to all gas appliances
- Remove items stored near boiler, cooker, or fire
- Ensure cupboard doors can open fully
- Move furniture blocking access if needed
- Make sure meter is accessible
Gather documentation:
- Previous gas safety certificate
- Boiler service records
- Appliance manuals and warranty information
- Note of any issues you've noticed
- List of appliances (if multiple or in different locations)
Check appliances are working:
- Turn on boiler to check it fires up
- Test gas cooker (if applicable)
- Note any pilot lights that have gone out
- Record any error codes or warning lights
On the day
Before the engineer arrives:
- Ensure someone over 18 is present
- Keep pets in a separate room
- Clear a workspace near appliances
- Have previous certificate ready to show
- Make sure all areas with gas appliances are unlocked
When the engineer arrives:
- Ask to see their Gas Safe ID card
- Verify the photo matches the person
- Check the card is current (not expired)
- Confirm it lists the work types they'll be doing
Taking a few minutes to prepare properly can save time during the inspection and prevent the need for a second visit. Engineers appreciate accessible appliances and clear workspaces - it helps them work more efficiently and thoroughly.
What the engineer checks
Gas Safe engineers follow strict guidelines for safety inspections, checking specific aspects of each appliance and installation.
Gas meter and installation
The engineer will check:
- Meter condition and security
- Emergency control valve (location and operation)
- Gas supply pipework (routing, support, and condition)
- Tightness test (pressure test to detect leaks)
- Bonding and earthing of pipes
- Ventilation adequacy for meter location
What they're looking for:
- Gas leaks or potential leak points
- Corrosion or damage to pipes
- Poorly supported or unprotected pipework
- Blocked ventilation
- Unsafe or inaccessible emergency control
Each gas appliance (boilers, fires, cookers, etc.)
The engineer performs specific tests on every gas appliance.
Visual inspection
- Overall condition and cleanliness
- Signs of corrosion, damage, or deterioration
- Correct installation and positioning
- Ventilation grilles not blocked
- Data badge legible (showing appliance specifications)
Operating pressure and heat input
- Gas supply pressure to appliance
- Working pressure during operation
- Heat input matches manufacturer's specifications
- Ensures appliance receives correct gas supply
Combustion analysis
- Flue gas composition (measures CO, CO₂, O₂)
- Combustion ratio (air-to-fuel mixture)
- Ensures complete combustion (not producing dangerous CO)
- Flame picture (correct color and pattern)
Safety devices
- Flame supervision device (flame failure device)
- Thermostat operation
- Overheat protection
- High limit stats
- Pressure relief valves (where fitted)
Flue and ventilation
- Flue termination location and condition
- Flue integrity and support
- Flue flow test (ensures products expelled properly)
- Room ventilation adequate for appliance
- Air bricks and vents not blocked
Gas Safety Check vs Boiler Service: What's Different?
Gas Safety Check (CP12)
- •Safety-focused
- •Tests for dangerous conditions
- •Checks all gas appliances
- •Legally required for landlords
- •Typically 30-60 minutes
- •Results in CP12 certificate
- •£60-90 typically
Boiler Service
- •Performance-focused
- •Prevents breakdowns
- •Only covers the boiler
- •Recommended but not legally required
- •Typically 45-90 minutes
- •May include cleaning and part replacement
- •£80-120 typically
Bottom line: Many engineers offer combined packages that include both safety checks and servicing. This provides comprehensive coverage and is often more cost-effective than booking separately.
Documentation during inspection
The engineer records:
- Property address and details
- Landlord and tenant information (if applicable)
- Appliance details (make, model, location, type)
- Test results (pressures, combustion readings, etc.)
- Pass/fail status for each appliance
- Any defects found
- Remedial work required
- Date of inspection
Classification of findings:
- NCS (Not to Current Standards) - Advisory only, doesn't prevent use
- AR (At Risk) - Should not be used until repaired
- ID (Immediately Dangerous) - Must be disconnected immediately
During the inspection: What happens
A typical gas safety inspection follows a structured process.
Step 1: Introduction and credentials (5 minutes)
The engineer will:
- Introduce themselves
- Show their Gas Safe ID card
- Explain what they'll be checking
- Ask about any concerns or issues you've noticed
- Review previous certificate (if available)
You should:
- Verify their ID card matches their appearance
- Note their Gas Safe licence number
- Ask any questions about the process
- Show them to the first appliance
Step 2: Meter and installation checks (10-15 minutes)
The engineer will:
- Locate and inspect the gas meter
- Test emergency control valve
- Perform tightness test (pressure test on pipework)
- Check pipework routing and support
- Verify adequate ventilation
- Note meter location on certificate
What you'll notice:
- Engineer may attach gauge to meter
- May ask you to confirm gas supply hasn't been altered
- May open cupboards or access panels
- Takes measurements and notes
Step 3: Appliance-by-appliance inspection (15-45 minutes)
For each appliance, the engineer will:
-
Visual inspection (2-3 minutes)
- Check overall condition
- Look for corrosion, damage, or poor installation
- Verify ventilation is adequate
-
Operational tests (5-10 minutes)
- Turn on appliance
- Test controls and thermostats
- Measure operating pressure
- Check heat input
-
Combustion analysis (5-10 minutes)
- Insert flue gas analyzer probe
- Take readings during operation
- Calculate combustion efficiency
- Check for carbon monoxide production
-
Safety device testing (3-5 minutes)
- Test flame supervision device
- Verify safety stats operate correctly
- Check overheat protection
-
Flue tests (3-5 minutes)
- Visual inspection of flue
- Spillage test or flue flow test
- Check termination is safe
What you'll notice:
- Various probes and gauges attached to appliance
- Engineer takes time to let appliance heat up
- Multiple tests performed while appliance runs
- Notes and readings recorded throughout
Step 4: Documentation and explanation (5-10 minutes)
The engineer will:
- Complete the CP12 certificate
- Explain findings
- Highlight any defects or concerns
- Provide recommendations
- Answer your questions
- Provide copy of certificate
You'll receive:
- Signed CP12 certificate (paper or digital)
- Warning notices (if AR or ID issues found)
- Explanation of any required work
- Recommendations for maintenance
Typical Gas Safety Inspection Timeline
Engineer shows Gas Safe ID, explains process
Tightness test, meter check, pipework inspection
Detailed testing of each appliance (varies by quantity)
Complete certificate, explain findings, provide copy
How long does a gas safety inspection take?
Inspection duration varies based on property size and complexity.
Typical timings:
- 1 appliance (e.g., boiler only): 30-45 minutes
- 2-3 appliances (e.g., boiler, cooker, fire): 45-60 minutes
- 4-5 appliances: 60-90 minutes
- 6+ appliances or HMO: 90+ minutes
Factors that increase time:
- Difficult appliance access
- Multiple levels or separate annexes
- Old or complex appliances
- Issues requiring investigation
- First inspection (no previous records)
Factors that reduce time:
- Well-maintained appliances
- Easy access
- Previous relationship with engineer (familiar with property)
- Recent service records available
If the engineer finds issues requiring immediate attention (ID classification), the inspection will take longer as they must make the appliance safe. This might involve disconnecting it or capping the gas supply.
What happens if issues are found?
Not all inspections result in a straightforward pass. Understanding the classification system helps you know how to respond.
Classification system
Gas Safe engineers use a standardized classification system:
Immediately Dangerous (ID)
What it means:
- Poses immediate risk to life or property
- Must be disconnected or made safe immediately
- Cannot be used until repaired and re-certified
What the engineer must do:
- Turn off or disconnect the appliance
- Attach a warning label
- Report to Health and Safety Executive
- Cap gas supply if necessary
- Issue warning notice
What you must do:
- Do not use the appliance
- Arrange immediate repair by Gas Safe engineer
- Do not attempt DIY fixes
- Inform tenants of danger (if landlord)
Common ID issues:
- Gas leaks
- High carbon monoxide levels
- Flame burning outside combustion chamber
- Severe flue blockage
- Risk of explosion or fire
At Risk (AR)
What it means:
- Could become dangerous if conditions change
- Not immediately life-threatening but unsafe
- Should not be used until repaired
What the engineer should do:
- Advise not to use the appliance
- May turn off but might not disconnect
- Issue warning notice
- Explain the risks
What you must do:
- Avoid using the appliance
- Arrange repair as soon as possible
- Cannot re-let property until repaired (if landlord)
- Get re-inspection after repair
Common AR issues:
- Minor flue deterioration
- Inadequate ventilation
- Partially blocked flue
- Safety device malfunction
- Corrosion that could worsen
Not to Current Standards (NCS)
What it means:
- Doesn't meet current regulations
- Not dangerous to continue using
- Advisory recommendation only
What the engineer will do:
- Note on certificate as advisory
- Explain what doesn't meet current standards
- Recommend improvement when practical
What you should do:
- Consider upgrading when convenient
- Not urgent but plan for future
- May affect property value or lettability
- Can continue to use appliance
Common NCS issues:
- Old installation methods (but still safe)
- Ventilation below current standards (but adequate)
- Appliance nearing end of expected life
- Cosmetic issues that don't affect safety
Landlord continued letting property after AR classification
A landlord received an AR (At Risk) warning for a boiler with inadequate ventilation during a gas safety check. They arranged a repair appointment for two weeks later but continued to let the property in the meantime.
- ✗Continued letting property with AR appliance
- ✗Didn't inform tenants of risk
- ✗Assumed 'At Risk' meant 'okay for now'
- ✗Delayed repair to save cost
- ✗Tenant used the boiler daily despite AR warning
A tenant suffered carbon monoxide poisoning and was hospitalized. The landlord was prosecuted for breach of gas safety regulations and received a £15,000 fine plus £8,000 costs. They were also ordered to repay 6 months' rent to the tenant and faced a civil claim for damages.
'At Risk' means exactly what it says - the appliance is unsafe and must not be used. Landlords cannot let properties with AR or ID appliances until they're repaired and re-certified. The savings from delaying repair are nothing compared to the consequences of harm.
After the inspection
Receiving your certificate
What you'll get:
- CP12 certificate (Landlord Gas Safety Record)
- Paper copy or digital (PDF via email)
- Must be dated and signed by engineer
- Valid for 12 months from inspection date
Check the certificate includes:
- Your property address (correct and complete)
- All appliances inspected (none missing)
- Engineer's name and Gas Safe number
- Results for each appliance
- Any defects noted
- Date of inspection
- Next inspection due date
If everything passed
Landlords must:
- Provide copy to tenant within 28 days
- Keep certificate for 2 years minimum
- Keep proof of provision (signed receipt or delivery confirmation)
- Schedule next inspection (10-11 months recommended)
- Store securely (digital and physical backup)
Homeowners should:
- Keep certificate safe
- Note expiry date in diary/calendar
- Book next inspection when due
- Store with property documents
If issues were found
For ID (Immediately Dangerous) findings:
- Appliance will be disconnected - do not reconnect
- Get quotes from Gas Safe engineers for repair
- Arrange repair urgently
- Book re-inspection after repair
- Inform tenants and ensure they don't use appliance
For AR (At Risk) findings:
- Do not use the appliance
- Arrange repair within days, not weeks
- Cannot re-let property until repaired (landlords)
- Get re-inspection and new certificate after repair
- Keep warning notice as record
For NCS (Not to Current Standards) findings:
- Can continue to use appliance
- Plan upgrades or improvements for future
- Consider addressing before next annual inspection
- May want to budget for replacement if appliance is old
If your inspection identifies AR or ID issues, you won't receive a CP12 certificate (or it will note the issues). You must arrange repairs and a re-inspection. Landlords cannot legally rent a property with unresolved AR or ID gas safety issues.
Costs and what's included
Standard inspection costs
Typical costs:
- 1 appliance: £60-80
- 2-3 appliances: £70-90
- 4-5 appliances: £80-110
- 6+ appliances: £100-150+
Geographic variations:
- London and South East: +20-40%
- Rural areas: May include travel surcharge
- Northern regions: Often lower rates
What's included in the price
Standard gas safety check includes:
- Engineer's time and expertise
- All testing and measurements
- Use of calibrated equipment
- Visual inspections
- CP12 certificate
- Explanation of findings
- Warning notices (if needed)
Not included:
- Repairs or parts
- Servicing or cleaning
- Replacement components
- Return visits
- Carbon monoxide alarm installation
- Emergency callout fees (if urgent)
Combined packages
Many engineers offer packages including:
- Gas safety check + boiler service: £120-180
- Gas safety check + CO alarm installation: £90-130
- Full maintenance package: £150-250
Benefits of packages:
- Better value than booking separately
- Comprehensive property coverage
- Single visit saves time
- Often prioritized booking
Gas Safety Inspection Cost Calculator
Estimate the cost of your gas safety inspection based on property size and requirements.
London and South East typically 20-40% higher. Prices exclude repairs, parts, or remedial work. Always get written quotes before booking.
Common questions and concerns
Can I stay in the property during the inspection?
Yes, and for landlords, someone over 18 must be present. The engineer needs access to appliances and may ask questions about their operation or any issues you've noticed.
Will the engineer need to turn off my heating?
Yes, temporarily. They'll need to test appliances in operation, which means cycling them on and off. Your heating will be back on before they leave (unless an issue is found requiring disconnection).
What if I'm a tenant and the landlord hasn't arranged an inspection?
Request one in writing. If the landlord doesn't respond, contact your local authority's private rented sector team. You have a legal right to a valid gas safety certificate.
Can the engineer service my boiler at the same time?
If you've booked a combined package, yes. If only booked for CP12, some engineers can add servicing on the day for an additional fee. Ask when booking or when they arrive.
What happens if an appliance fails that I've just had serviced?
A service focuses on performance and maintenance; a safety check focuses on dangerous conditions. Both are important. A recently serviced appliance should pass, but issues can develop quickly, or the service might have missed safety concerns.
Do I need to test everything before the engineer arrives?
No, the engineer will test everything during inspection. However, noting any issues helps them investigate problems more efficiently.
Frequently asked questions
Legally, you must give 'reasonable notice' which is typically interpreted as 24-48 hours in writing. Best practice is to give a week's notice and offer several appointment times to accommodate the tenant's schedule. Document all communication in case access becomes an issue.
Yes. Clear access to all gas appliances, ensure cupboards and panels can open fully, move any stored items away from the boiler or meter, and have your previous certificate ready. Good preparation can save 10-15 minutes and makes the engineer's job easier.
If a gas appliance is connected to the gas supply, it must be safe even if not in use. The engineer must check it and will classify any issues. You can permanently disconnect appliances you don't use (must be done by a Gas Safe engineer), after which they don't need annual checks.
No, a gas safety check is inspection-focused, not maintenance. They check for safety issues but don't clean heat exchangers, replace worn parts, or optimize performance. That's what a service does. Many engineers offer combined check-and-service packages.
The CP12 certificate covers all gas appliances in the property. You can't get a certificate for just one appliance while excluding others. If you only have one appliance, the certificate will list just that one. If you have multiple appliances, all must be checked.
All gas work must be done by Gas Safe registered engineers. If a tenant has installed a gas appliance, it must be professionally checked immediately. You remain legally responsible for all gas appliances in your property regardless of who installed them. Consider prohibiting tenant installations in your tenancy agreement.
Landlords must provide the certificate before you move in, or within 28 days of the inspection if it's done after you move in. If you don't receive it within 28 days, request it in writing. If the landlord still doesn't provide it, contact your local authority.
Most engineers offer morning/afternoon slots or time windows (e.g., 9am-1pm). Exact times are harder to guarantee due to variable job durations. If you need a specific time (e.g., due to work commitments), discuss this when booking - some engineers accommodate this, possibly with premium pricing.
Next steps
Learn about your legal obligations as a landlord:
Landlord Gas Safety Responsibilities →
Understand the certificate you'll receive:
Gas Safety Certificate Explained →
Find a qualified engineer for your inspection:
How to Find a Gas Safe Engineer →
Ready to book your gas safety inspection? Gas Safe registered engineers can typically schedule checks within a few days and provide certificates immediately after completion.
Related articles:
Useful resources:
- Gas Safe Register: 0800 408 5500
- Gas Emergency: 0800 111 999
Tools: