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Common Questions - Pro-Duct Clean Ltd - Air Duct Cleaning Specialists =


  1. What is General Ventilation?
  2. Why is Fresh Air Required in the Workplace?
  3. When do I need to Clean my Ventilation System?
  4. Is it Necessary to Clean New Ductwork Before Use?
  5. How Can I specify the Service I Require from a Ventilation Cleaning Company?
  6. What Certificate(s) do I get for Air Duct Cleans?


What is General Ventilation?

General Ventilation (or dilution ventilation) is a term used to define the flow of air into and out of a working area, for example and office space, so that any contaminants are diluted by adding some fresh air. This can be provided by:

  • Natural ventilation which relies on wind pressure and temperature differences to move fresh air through a building and is usually not fully controllable.
  • Forced or mechanical ventilation which uses mechanical supply and/or extraction to provide fresh air and is controllable.
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Why is Fresh Air Required in the Workplace?

You need to provide fresh air to:

  • provide oxygen for breathing in and to remove carbon dioxide from breathing out;
  • remove excess heat or, if conditioned, provide heat (e.g. in winter) and keep a comfortable temperature;
  • dilute and remove body and other types of odours (e.g. food); and
  • dilute any contaminants caused by workplace activities (i.e. the use of dilution ventilation following a risk assessment).

Insufficient fresh air may lead to tiredness, lethargy, headaches, dry or itchy skin and eye irritation in your employees. These symptoms may also be produced whilst working in poorly designed buildings and offices and when there are unsatisfactory working conditions. The symptoms are generally worse in buildings where there is not enough fresh air, or where the fresh air supply may come into contact with contaminants in the air supply system. These are common symptoms of what is generally known as sick building syndrome.

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When do I need to Clean my Ventilation System?

The Approved Code of Practice to Regulation 6 of the Workplace (Health Safety and Welfare) regulations 1992 requires that any mechanical ventilation systems, including air conditioning systems, which you use to provide fresh air should be regularly and properly cleaned, tested and maintained to make sure they are kept clean and free from anything which may contaminate the air and cause health problems.

As a general rule, if you run your finger along the opening of a duct and it collects dust then it probably needs cleaning. Organisations such as the Heating and Ventilation Contractors Association (HVCA) and the Chartered Institution of Building Services Engineers (CIBSE) provide information on testing for likely contaminants in ductwork and on cleaning. As an HVCA member, Pro-Duct Clean Ltd can also provide you with impartial advice and guidance.

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Is it Necessary to Clean New Ductwork Before Use?

Building sites are dusty, dirty places so it is very difficult to prevent any new installation of ductwork from becoming contaminated with the likes of brick, cement and plaster dusts, never mind mineral fibres, forgotten sandwiches and hard hats!

Capping-off the ducts is often used as a potential solution, but even then it is not necessarily fool-proof - and it does add significant additional expense. It is practically impossible to keep ductwork clean by 'capping off'; partly because you have to have the system open in order to erect new duct sections, and that is during the busy, dusty, daytime site working periods. What is more: site people have a strange desire to 'pop' the covers!

The HVCA Guide to Good Practice TR19: 'Cleanliness of Ventilation Systems', aims to provide some clarity.

Firstly, the specifier's need to decide what they want and specify it clearly. Three levels of protection listed in TR19. The third, highest level requires cleaning by a specialist contractor after installation. Given that it is practically impossible to keep ductwork clean by 'capping off', if you want to operate a clean system, then in reality the only objective choice is to specify cleaning.

Secondly, it is important to be clear as to the appropriate measure of cleanliness level for new systems. It is more appropriate to specify against the Post-Clean verification level (0.075g/m2) than using the Surface Deposit Limits ( 6g/m2 for extracts and 1g/m2 for supply and recirculation ducts), since the latter (Surface Deposit Limit) is really a measure of dirtiness, i.e. a 'trigger' level designed to advise when an existing system in use, has become so dirty that it should be cleaned.

So, clearly if you are starting off a new system, you really do need to do a thorough job in minimising the potential for adverse reaction from the new occupants (especially when combined with a cocktail of VOC's off-gassing from adhesives, coatings and other components) is immense, and experienced often enough. You can imagine the frustration of the Facility Manager who has just spent a fortune on building/renting/moving into new premises!

To summarise, the advantages in accepting from the outset of a new build that the system will be professionally cleaned before being brought into use include;

  • You can verify and fine-tune the access system for cleaning
  • You can save a fortune by dispensing with excessive capping off
  • Most importantly in practice, it gives the project people certainty: if a specifier ducks the issue and simply says 'install the ductwork cleanly', without measurable post-clean verification limits to achieve, then who decides what is clean? It's a recipe for under-cutting at tender stage, and conflict throughout the construction and handover stages
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How Can I specify the Service I Require from a Ventilation Cleaning Company?
  BSRIA Standard Specification for Ventilation Hygiene

For most of us, setting up a robust, yet appropriate specification for a specialist service such as cleaning and maintenance of an air conditioning or ventilation hygiene system from scratch would be a considerable challenge.

Fortunately, the Building Services Research and Information Association (BSRIA) has written a Standard Specification of Ventilation Hygiene, which is intended to provide the basis for a ventilation hygiene contract between a Client and a Contractor.

You can order a copy of the specification and accompanying Guidance directly from the BSRIA bookshop.

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What Certificate(s) do I get for Air Duct Cleans?

Unfortunately, there are currently no universally standard certificates that can be issued in the UK for Air Duct cleaning as a guarantee of meeting a consistent standard (as you would get when you take a car for an M.O.T. test, for example).

However, there are number of well documented Standards and Best Practice Guides issues by reputable industry bodies such as the Heating and Ventilation Contractors Association (the HVCA), and members of the HVCA will be able to issue you written confirmation that they have performed a job in accordance with a particular standard, and this may well be in the form of a Certificate.

For example, With the introduction of the Fire Safety Order - the Regulatory Reform (Fire Safety) Order in 2005, it is now the owners and managers of premises who carry the full responsibility for ensuring the safety of building occupants - a role which before October 2006 was effectively carried out by the Fire Authorities by issuing Fire Certificates.

So, with an Extract System, any body with a staff or custom of more than five people has to, by law, complete a Fire Risk Assessment. A component part of that is a certificate to confirm that their Extract including the Duct has been cleaned by a company 'fit for purpose'. The term 'fit for purpose' is now interpreted as at the very least requiring that the cleaning company should be an HVCA member that adheres to the TR/19 standards. To be a member of the HVCA a company has to have been trading for at least three years and pass an independent audit for methods and systems.

Similarly, following other types of cleaning, such as an Air Duct Deep Clean, the cleaning company may issue a certificate stating that the work has been done and saying how long it is valid for, and against which standards the cleaning has been completed. However, as mentioned above, there is currently no single universal standard for this certification.

To conclude, in the absence of proper standardisation, you are best advised to find a cleaning company with a good track record who is a member of a reputable trade organisation such as the HVCA, and who will give a written certificate to confirm that the work they have undertaken follows the most appropriate standards and guidelines. The chances are that your insurance company will require this anyway.

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