Tuesday, 20 May 2014

Ventilation System Testing Methods

Carrying out regular ventilation system testing to keep air supplies clean and safe is a vital task which requires specialist knowledge and experience. Tecomak regularly tests the ventilation systems used in many different environments. These range from medical and educational facilities to research laboratories and industrial plants.

We use different testing methods to suit the particular type of ventilation system, including those used for clean processes and those used to control hazardous substances  such as fume cupboards and LEV systems. Our fully qualified, professional engineers carry out tests in accordance with all relevant regulatory standards, and can also issue certificates. Here is a look at some of the methods used.

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Air Change Rate Measurements

Air change rates are a key measurement of airflow performance of a controlled space. Higher air change rates will dilute airborne contaminants more quickly ensuring protection of the occupants or process being performed in the space. In cleanroom facilities this is one of the tests used to validate rooms licensed by the MHRA for pharmaceutical production. It is also used to test hospital ventilation systems to ensure bacteriogical contaminants are kept below a safe level. In laboroatires and chemical storage areas  minimum air change rates are recommended to ensure background levels of hazardous fumes and vapours are controlled well below the statutory exposure limits.

Air change rate measurements require the room volume to be determined and the volume flow rate of air entering (via ceiling grilles for example) or being extracted from the room (via fume cupboards) the room to be measured. 

The air change rate is simply the flow rate, often recorded in cubic metres an hour  divided by the volume of the room.

Differential Pressure Testing
Differential pressures between rooms within a facility ensures clean spaces remain clean and dirty or contaminated spaces do not spread contamination to surrounding areas.  A cleanroom will be maintained at positive pressure to surrounding areas whilst a containment laboratory will be maintained at a negative pressure.

It is essential that in any clean room the air moves in the right direction with the air pressure pushing out from the clean room to non-sterile areas outside, rather than in the opposite direction, which could risk bringing in contamination.

A containment laboratory however works in reverse having a relative pressure below surrounding areas to ensure any air leakage is into the lab and not out which could result in the escape of a hazardous substance.

Differential pressure measurements are taken using a micromanometer and the unit of measurement is a Pascal.

Biological Sampling
Medical facilities such as operating theatres are among the premises where biological sampling is vital. It is often  carried out as part of the annual HTM 03-01 verification of ventilation systems in these settings. Sampling can be carried out remotely while the operating theatre is empty and again when it is in use. One of the methods used is active air sampling, which monitors levels of micro-organisms in the air, while another is settle plate sampling. Biological sampling is also needed in pharmaceutical research laboratories and clean rooms

Filter Testing

HEPA filters are used within a  ventilation system to remove airbourne particulate (fine dust) and particules that maybe be harbouring microbilogical contaminants. They are fitted to both air supply systems  to ensure air quality entering a cleanroom for example but also of extract systems fitted to safety cabinets and containment laboroatroes.HEPA filters are fragile and can be easiliy damaged or disturbed susch that air quality is not maintained at its intended level. Reguare integrity testing is therefore required for compliance.  HEPA filters are scan tested with a photometer or particle counter to ensure there are no local leaks across the face of the filter caused by media damage or around the perimeter due to a damaged seal or incorrect fitment within its housing.  The most common test standard being ISO 14644-3:2005.

Carbon filters are used to remove hazardous gases and vapours usually on exhaust systems from fume cupboards. They also require regular testing to ensure they have adequate efficiency. The type of test conducted will depend on the substance(s) being controlled. In the case of re-circulating fume cupboards BS7989:2001 provides suitable test procedures.

Airflow Pattern Testing / Airflow Visualisation
Airflow pattern testing or visualisation is an important qualitative means of assessing the effectiveness of a ventilation system in a local area of controlled zone. For example, Local exhaust ventilation (LEV) systems need to be checked that they fully capture the hazardous emission being controlled. Often air velocities measurements will not detect eddies, turbulence and reverse flow that can be readily identified by means of visualisation.

Airflow Velocity Measurements
Airflow velocities are a quantitative means of determining ventilation performance and often acceptance critiera will be specified by the relevant standard. The HSE for example recommend minimum airflow veloicities for LEV systems in their guidance document HSG 258.

Airflow velocities are measured in the ductwork of a system to accurately determine flow rate.

Inspection of Physical Components
Visual examination of the various components is an important part of the ventilation system appraisal process. LEV systems (this includes fume cupboards and safety cabinets) must be thoroughly examined atleast every 14 months for compliance with the COSHH regulations.  Other test standards will make specific reference to the scope of the inspection with fume cupboards used in schools, under Building Bulletin 88, we need to visually inspect both the cupboard structure, sash system,  services and the complete extract system. In the case of ducted industrial fume cupboards BS EN 14175 Part 4 defines the inspection and maintenance requirements. 

Inspection and Calibration of Alarm Systems

Airflow monitoring alarm systems within ducted industrial fume cupboards  and other LEV systems need to be regularly checked for correct operation and calibrated when required. The same applies to room pressure alarms installed to microbiological containment laboratories, and any other facility where monitoring alarms have been fitted to warn of potentially hazardous low airflow or room pressures. As well as carrying out calibration of n alarm systems, Tecomak can also carry out upgrades and install new systems  where necessary.

Consistent and accurate ventilation system testing is crucial to the safe and reliable operation of all systems that protect occupants, the environment or quality assured products and research.

System owners need to be confident that the people carrying out the testing are competent and have sufficient expertise to provide the best advice and guidance. Tecomak have highly trained, experienced and fully qualified staff who can test all your systems, so there is no need to call in a number of different contractors. We are also able to combine testing with ventilation system maintenance and certification, thus minimising any downtime.

Ventilation System Maintenance – Contact Tecomak to find out how we can help your organisation.