System Hygienics are the UK market leaders in ventilation hygiene and now one of the largest specialists in the world.
Established in 1993, we are certified members of the US National Air Duct Cleaners Association (NADCA) and founding members of the Ventilation Hygiene Specialists Branch within the Heating and Ventilation Contractors Association (HVCA).

Our services are provided from strategically located depots in the UK and by special arrangement overseas.

The Air Hygiene Division the unique JetVent system of Cleaning, specialising in the inspection, monitoring and cleaning of HVAC systems, complements the Kitchen Extract Division which specialises in monitoring and cleaning grease-affected air systems.

We are a member of the Hotchkiss Group of Companies which provides specialist services in the field of ventilation, air conditioning, fire protection and environmental sectors through subsidiaries Hotchkiss Ductwork Ltd, Fire Protection Ltd, Hotchkiss Air Supply Ltd, Firespray International Ltd.

All site operatives and project managers have been accredited with the Engineering Services SKILLcard scheme detailing the training, competencies in Health and Safety, Confined Space, Mobile Platforms, Scaffolding and in some cases Industrial Rope Access Techniques. System Hygienics holds a Gold award from the SKILLcard scheme, has Chas accreditation and is registered with Constructionline.

Ductwork. Out of sight. Out of mind.

Cleanliness and safety... the essential ingredients of every well-managed kitchen. At the heart of the matter is your kitchen extract system, the perfect landing place for grease, oil and other deposits.

Keeping canopy hoods and filters regularly cleaned is the easy part. But what happens to the ductwork, the part you cannot see.

Failure to deal effectively and comprehensively with this issue is just storing up problems...

Fire Risk

A Fire Waiting to Happen
Extraction system filters can never eliminate all vapourised grease which, together with debris, condenses onto the canopy plenum, duct and fan surfaces. This build-up now only requires heat - readily available in every kitchen - to trigger off a frightening process. A spark or flame is not necessary, as spontaneous combustion can occur.

The grease in the duct acts as a fuse, carrying fire through the duct and the building. Fire, smoke and hot gases may break out at any penetration, hole, joint or discharge point or following heat-induced collapse of ductwork.


Temperatures up to 1200degC transmit heat through the metal to distort, destroy or ignite nearby material... such as duct support hangers, packing materials, electrical systems and litter.

In this way fire can spread rapidly... following the duct route which may be difficult and dangerous for fire fighters to access.

A Risk Too Far
The Insurance Industry is hardening its attitude on the issue. This is hardly surprising since The Association of British Insurers has recorded losses associated with dirty kitchen extract fires rising from £25 million in 1997 to £65 million in 1998. (N.B. This only takes account of direct losses in excess of £50,000).

The Insurers' Loss prevention Council recommend that at least annual cleaning of entire systems by specialists is carried out, the exact frequency to be determined by a reasoned risk assessment.

Failure to comply with the terms of a policy could mean invalidation of the entire contract, leaving the insured to carry a total loss. ... "The overwhelming important factor is inadequate cleaning of ductwork..." Mark Newton, Royal and Sun Alliance.

Other Problems

Something in the Air
Warm, grease laden ductwork is a breeding ground for micro-organisms. It attracts vermin. When systems are shut off, dirty air and odours can backwash into the kitchen area. Rancid odours may be discharged into the environment resulting in neighbour, landlord and environmental health complaints, never mind the effect on your customers.

Mechanical Efficiency Compromised
Build-up of grease can seriously compromise your systems efficiency in a number of ways such as affecting the fan impellor and scroll. Clogged ductwork and components, affect the removal of hot, grease- laden and odorous air... with reductions in airflow of up to 26% recorded. Jammed fans leading to system failure are not uncommon.

Health & Safety Issues
The health and performance of kitchen staff can be badly affected when heat, moisture, cooking and combustion products such as unburnt gases and carbon monoxide are not effectively removed.

In such an atmosphere, the risk of accidents - in an already high risk environment - is significantly increased.

Inspection and Testing

It is a fact that hundreds of thousands of systems are not properly cleaned.

Kitchen extract cleaning is a fundamentally difficult and dirty job. No-one wants to do it. Busy caterers do not possess the knowledge or the time to check that the work is properly carried out.

The heart of the problem is that ductwork is difficult to access. You can see the canopy, and maybe the fan. But if you cannnot see or easily reach the ductwork interior, the odds are that it has not been cleaned.

Inspection surveys have shown that, even when a cleaning contractor is employed, up to 90% of the system is not actually cleaned.

What caterers demand is a reliable, specialist contractor to the access that is needed, and clean the ductwork properbly to HVCA TR19 Good Practice Standards.

Certifiable Standards

Cleanliness standards that we achieve are verifiable through wet film or deposit thickness testing. A certificate can therefore be issued, based on results which can be repeated and audited.

The certificate has real value and authority... to customers, their insurers and health & safety inspectors.

Service reports are provided to include comment on any other aspects of kitchen extract safety and operation. Photographs can be issued or stored for audit purposes.

Quality Assurance
We take our responsibilities seriously and recognise the potential consequences of unprofessional cleaning. A rigorous cascade system of quality management is operated at every level from operative to senior management.

Additionally our service quality is tested by customer questionnaire to ensure continued satisfaction.

Air Hygiene Division

Something in the Air...

Clean, fresh air in buildings is the key to safe, comfortable and efficient working conditions.

An essential factor is that the heating, ventilation and air conditioning (HVAC) ductwork systems must be kept clean.

Inevitably all duct systems become fouled over a period of time. The rate and severity of contamination can be attributed to a number of factors. However it is possible to deal with these issues through a sensible programme of hygiene maintenance. problems...

Fouling of Air Systems: The Cause...

The quality of filters and their ongoing maintenance is crucial to the rate of fouling in supply air systems. No filter - even a HEPA filter - is truly absolute. The speed of fouling will vary in relationship to the grade of filter being used.

All too frequently newly installed ductwork systems are left in a dirty state due to the presence of builder's dust and rubble.

The location of the building and its plantrooms also has a direct bearing on the air quality provided through the HVAC system. Each local environment will be affected by its own peculiarities...from combustion products, including chemically laden particulate, to allergenic organic matter and high humidity.

For buildings in which used air is recirculated, a further range of contaminants will affect air quality, including skin flake, textile fibres, paper dust and pollutants specific to any work process.

The HVAC system can generate its own range of contaminants...rust, corrosion, insulation material and filter media, together with micro-organisms associated with moisture sources.

Extract or return air systems are generally not filtered. Therefore dust, fibres and other contaminants generated throughout the building will accumulate over time.

The Effects...
On People

Most of us spend the majority of our time living and working in a built environment. Most products are also manufactured in a similar environment which can be equally vulnerable to poor air hygiene.

Air distribution systems concentrate surface contaminants within the plant and ductwork, and as a result conditioned air can be affected. Air can be degraded by odorous, irritating or hazardous volatile organic compounds off-gassing from dirt deposits or associated micro-organisms.

Dust and dirt in air systems can provide a favourable nutrient for micro-organisms. If moisture is present (eg leakage, condensation, carry-over or even high relative humidity) then explosive microbial growth can occur. In the worst scenarios, visible dirt particles comprising agglomerations of finer dusts can be emitted from grilles and diffusers.

Complaints from occupants range from chronic, low-level dis-satisfaction through to acute health effects. Odour and perceived dirtiness of the working environment can further contribute to poor morale and de-motivation.

On Efficiency
Fouling can severely compromise the mechanical efficiency of air systems by clogging of heat exchangers, blinding of sensors, interference with volume and control dampers, frictional losses and reduction in cross-sectional area.

Recorded reductions in airflow - up to 66% in extreme cases - can result in occupants not receiving air in either the correct volumes or the correct condition.

Cumulative increases of 5% per annum in energy consumption can be caused by fouling of air systems.

On Safety
Accumulated dust and debris in ducting systems forms a hidden combustion load, presenting a real fire hazard.

Legislating for Cleaner Air

The demand from occupiers for a clean, safe environment, coupled with liability, legislation and insurance issues, is reflected in an increasingly coherent body of legislation and authoritative guidance throughout the world.

Enlightened employers and landlords recognise the potential productivity, efficiency and comfort benefits of operating clean, safe systems.
The Workplace (Health, Safety and Welfare) Regulations 1992 require mechanical ventilation systems to be maintained (including cleaning as appropriate) in an efficient state, in efficient working order and in good repair.The accompanying Approved Code of Practice states that: "Mechanical ventilation systems (including air-conditioning systems) should be regularly and properly cleaned, tested and maintained to ensure that they are kept clean and free from anything which may contaminate the air."

Further specific obligations flow from amongst others the Control of Substances Hazardous to Health(COSHH) and Management of Health and Safety at Work Regulations, Food Safety Act and Occupiers Liability Act 1984.

Authoritative technical guidance on how to define system cleanliness and to establish a systematic maintenance regime is provided by the HVCA Guide to Good Practice TR19: Internal Cleanliness of Ventilation Systems. Further guidance is provided by BSRIA, CIBSE and the Health and Safety Executive.

Taking Action

You should firstly satisfy yourself on the current condition of your air systems. The TR 19 Guide to Good Practice provides a benchmark on which a system's condition can be assessed before planning any obvious necessary remedial work.

A suitable system of maintenance should be instigated to include hygienic testing of the ventilation system's surface and indoor air quality (IAQ).

Records should be kept to validate the maintenance regime, to provide early warning of potential defects and to demonstrate that clean systems are being operated.

New Build
Pre-commission cleaning ensures that new systems are clean from the word go.

Refurbishments
Cleaning, rather than replacing duct distribution systems, can produce cost savings in excess of 95%, in addition to time and disruption benefits.

Air Hygiene Services

In the UK and worldwide, System Hygienics are at the leading edge of the Air Hygiene business through the application of specialist experience, expertise and new technology. We are in the business of providing a comprehensive package of cost-effective solutions...

Air Hygiene Risk Assessment Survey
Investigation into the hygienic state of air conditioning and ventilation ductwork using state-of the art enabling techniques...robot video camera, endoscopic photography and instant read-out dust measurement.

Third party laboratory analysis and established inspection and testing protocols provide verifiable and repeatable survey results.

Environmental Hygiene, Comfort and Safety Survey
Specialist appraisal and remedial advice of the total building hygiene and comfort conditions, including thermal comfort, ventilation rate and airflow patterns, noting any airborne contaminants.

Air Distribution System Cleaning
We employ safe, effective and convenient methods for cleaning ductwork. Using the pioneering Jetvent(tm) technology, up to 100 metres of duct is cleaned remotely from one access point...reducing the number of access points required and minimising potential disruption to ceilings.

Verifiable cleaning performance measurement, including a cascade approach to quality assurance gives full confidence that a complete, effective clean has been achieved.

Environmental Hygiene Management Programme
An agreed programme of regular environmental hygiene checks including measurement of airborne, surface and waterborne micro-organisms, dusts and gases. Established techniques ensure close monitoring of indoor air quality.

Hygiene maintenance procedures such as cleaning and disinfecting air handling units, cooling coils, humidifier and duct components are carried out at fixed frequencies through the year or based on condition monitoring.

Regular reports, compiled in a site log, provide a single reference point and assurance that critical tasks are in the hands of specialists.

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