Feeling the Draught

Feeling the Draught

Commissioning of an appliance is a vital part of the installation process and a draught gauge is a really important item to hold in your tool kit to ensure the job is done properly. Here are some top tips on getting it right.

Flue Draught Test

The constant flow of flue gases at the correct rate of flow with the least possible variation is required for safe and efficient combustion. Insufficient flue draught will cause ignition difficulties and is likely to result in fume emission and a potential health risk. Too much draught will make control of the fire difficult and may result in overheating.  In this instance, fitting a draught stabiliser may be required. An appliance manufacturer will specify a range of flue draft conditions under which their appliance will operate.

Flue draught readings can be taken using a purpose made flue draught gauge or using any suitable pressure differential measurement device. See our examples later on in the article.

The correct place for measuring the chimney draught is close to the appliance and at least 150mm away from any draught regulator. Sometimes this distance may also be described as two times flue diameter.

Some appliances include purpose-made flue draught test points for test equipment sampling probe insertion. If no purpose-made point exists, a suitable point will need to be provided adjacent to the appliance outlet. In some instances a draught measurement can be taken by temporarily removing a sweeping access cover and using a cone or plate with a hole in the centre to prevent secondary air entry and enable insertion of the sampling probe. A flue draught reading should be taken before the appliance is lit to identify potential problems which could result from down draught.

Procedure for Taking Flue Draught Readings

The typical procedure when using a purpose made mechanical draught gauge as shown in Fig 30 is as follows:

1.   Visually inspect the draught gauge for signs of damage and/or defect.

2.  Ignite a small amount of fuel in the appliance and leave to burn for 20 minutes.

3.   Adjust pointer to zero (before each measurement).

4.  Position the gauge on a level base or hang upright.

5.   Insert metal sampling tube into test point preventing secondary air entry.

6.  Wait approximately 30 seconds for stabilisation and then take the draught reading.

7.     Take the reading every 10 minutes until the maximum draught is reached

Please Note: Atmospheric or weather conditions may cause incorrect draught readings.


Depending upon the draught reading obtained, it may be necessary to adjust the appliance air control devices and/or the flue draught stabiliser (if fitted). Any adjustment should be made in accordance with the appliance manufacturer’s instructions and the draught should be reading retaken after each adjustment.

If acceptable draught conditions are not able to be achieved, the appliance should be taken out of service and where appropriate the HETAS unsafe situations procedure (see HUSP form below) should be followed while the fault is rectified. Refer to Appendix E in the back of this Unit for more details.

Testing & Commissioning

Unless you have to leave a warning notice, a summary successful maintenance report for your customer will add a level of professionalism and give reassurance that you are leaving the installation in a safe state. A signed and dated testing & Commissioning sheet should offer the following as relevant:

·         Confirm operation status as per manufacturers requirements.

·         Confirm or detail non-compliance with current requirements.

·         Check the CO Alarm is operational and correctly positioned.

·         To check/confirm the condition of the “hidden seals” within the appliance carry out Smoke Test I.


·         Smoke Draw Test (Smoke Test II). This should be carried out with all the doors and windows closed in the room in which the appliance is installed.

·         Confirm flue draft readings are as per manufacturers requirements.

·         Ensure end user is confident in the continued use of the appliance.

·         Complete appropriate paperwork and where necessary obtaining customer signature and leave a copy with the customer.

Draught Gauges

HETAS currently has three draught gauges available in the HETAS Shop.


HETAS have produced the Unsafe Situation Procedure Assessment Form to help installers assess whether an installation is to be deemed unsafe and lists the re-commisioning checks needed if the installation is found to be compliant.

Visit the HETAS Technical Area for further information on the HUSP.


HUSP goes live

HUSP goes live

HUSP goes liveOver recent months, HETAS has been looking at the ways in which it can support its stakeholders further when identifying installations that may pose a significant risk to either the properties occupants or ongoing fire safety of the buildings structure and we are pleased to announce that HUSP has now gone live.

 Calvin May, Technical Standards Manager at HETAS introduces the new HETAS Unsafe Situations Procedure (HUSP) to aid identification of risks with a re-commissioning checklist.

What is HUSP?

The HETAS warning label process is currently available to identify scenarios that pose an immediate risk, however there are certain circumstances whereby the installation does not follow the current Building Regulation guidelines or will pose a significant risk under continued use of the appliance that requires a further assessment and decision on what protocol to follow.

With this in mind, HETAS has gone on to develop an industry recognised “Unsafe Situations Procedure”, to formulate a new process in which to identify all areas of potential risk within an installation following UK Building Regulation guidelines and requirements of UK applicable standards.

The procedure will allow for the engineer to identify and take the appropriate action where required to negate the area of risk and appropriately report their findings to either relay to the consumer or evidence as a means of carrying out further remedial works. As with most assessments, the procedure works on the basis of using the engineer’s competence, experience and training to identify potentially hazardous scenarios, however provides effective tools in which to make judgement and evidence the reasoning behind these judgements, and to record with written consent from the consumer.

HUSP encourages an appropriate assessment to be made in all cases, and appropriate action to be taken defined against three classification categories:

  • Assessed Risk Low – typically categorised as those installations that have installation techniques that fall outside the current scope of Building Regulation guidelines and relevant standards, however can be seen to have been working correctly without risk for a number of years.
  • Assessed Risk High – installations that at the current time of assessment have been assessed and deemed to contain risk but not immediate risk. However continued use of the appliance over time will result in danger to the occupants and/or the property.
  • Immediately Dangerous – as written within the current Warning Label process, a dangerous appliance or installation which poses an immediate danger to the occupant of the property at the time of assessment.

To aid installers further, the procedure provides some additional guidance of some of the more common installation scenarios, as well as a guided risk category score in which to make judgement against, and will be continually developed as new situations and innovation advances over time.

HUSP Guidance

What does the assessment cover?

The assessment covers the 5 main areas of the Building Regulations J1 to J5, including ventilation, dispersion of products, CO activation and protection of building, as well as some of the caveats contained within BSI installation standards BS8303 and BS EN 15287-1. The assessment will also need to consider the characteristics of the property and whether any energy efficiency changes have been made over the years (improved insulation, cavity wall, and draught excluders), so communication with the consumer, visual checks and appropriate testing are essential to formulate the required point of action.

The assessment form available is a simplified reference point on what to look out for when at the property in compliance with Building Regulation guidelines, as well as the appropriate re-commissioning checks to carry out and signed declaration of the results. All installations would need to be left in safe circumstances through confirmation of the appropriate smoke test, flue draught extraction tests and spillage tests, all guidance of which to perform and carry out this testing is contained within the electronically supplied document.

Appropriate Action

HETAS will continue to make its warning label available, which can be attached to the appliance should any situations be found to contain risk of an immediate nature, advising the consumer not to operate the appliance further until required remedial works have been undertaken. The form will now contain details of the assessment undertaken, defects identified and outcomes in which to discuss with the consumer to ensure an understanding of what needs rectifying is discussed and agreed.

Further Information

Further information and supporting documentation as always can be found in the Technical Area of the HETAS website, or call the HETAS technical helpline on 01684 278194 (please have your HETAS Registration number to hand).