Airflow ventilation system performance

Reliability of airflow measurements m assessing ventilation systems performance Cobalt - a review of properties, use and levels of exposure A review of respirable crystalline silica - Exposure and control... 

Portions of the HCF structure, along with the steel confinement boxes (SCBs), gloveboxes, fume hoods, and the ventilation systems perform confinement functions. These confinement systems provide defense in depth by ensuring that hazardous materials are retained in specific designated areas within the HCF. They accomplish this function by maintaining an air pressure differential hierarchy from regions of greater contamination to those of lesser contamination within the facility. These differentials are described later in this section. This pressure differential controls the movement of contamination by diffusion and by adverse airflows. The Identified contamination zones in the HCF are as follows ... 

Proper design and construction of a local ventilation system must account for hood flow rate, contaminant generation process and rate, and the generated flow rate of contaminated air. Thus, knowledge about airflow mechanics, process performance, and the contaminant source is essential. The descriptions of different sources are included in Chapter 7 and here only short descripiions are included as necessary to identify different processes and source types. 

The initial performance test for all local ventilation systems is a smoke test, which provides easy airflow visualization between the source and the hood, it helps to identify, with little effort, the main features of airflow patterns. Such a test, recorded by a video camera, allows performance comparisons to be made before and after improvements. Real contaminant or tracer gas measurements are necessary in the case of more detailed testing. 

For ventilation systems a separate study named AIRLESS was performed [30,55]. Experiments were performed to investigate why, when and how the components of HVAC systems pollute or are the reason for pollution. Different combinations of temperature, relative humidity, airflow and pollution in passing air were investigated. Measurements of perceived air quality, particles, chemical compounds (such as very volatile organic compounds and aldehydes) and biological compounds were selected for each component. The most polluting components of HVAC systems were studied in the laboratory and in the field. The perceived air quality or odour intensity was in most cases measured with a trained sensory panel, according to the protocol developed for the AIRLESS project (Sect. 3.2). 

A TSR requirement to verify that Zone 1 and Zone 2A ventilation exhaust HEPA and charcoal filters are in-service vwll be implemented to assure that exhaust gases are being filtered when the HCF ventilation system is in operation. A TSR requirement to verify the ventilation system fan sequencing interlock is operable vvnil be implemented to ensure that proper building airflow patterns are maintained in the event of exhaust fan failures. The ventilation system exhaust ducting provides only an inherent passive safety function (i.e., confinement) and no specific TSR controls are required to ensure continued performance of this function. 

It is important not to disturb the performance and airflow pattern of the fume cupboard. Staff standing or walking in front of the fume cupboard will disturb the air exhaust. The operator must have sufficient space in front of the fume cupboard to work easily and comfortable. Room doors that open frequently during operation in a fume cupboard and (strong) inflowing air fi om the room ventilation system (in the direction of the fume cupboard) may have a negative impact on the performance of the fume cupboard. Airflow visualisation with smoke is illustrative and often necessary. 

In addition to the testing of the airborne concentrations of pollutants, it is necessary to check airflows and pressures created in a ventilation system to ensure that it is working to its designed performance by measuring ... 

Building ventilation networks are systems that serve multiple locations. The common practice of arbitrarily adjusting the dampers or baffles to accommodate complaints from one area must be avoided. By changing the airflow in one area, the system balance is shifted and distribution throughout the entire network is affected. If there are distribution complaints, a test of the building s air-handhng system should be performed to confirm that the HVAC system and distribution network are in balance and are adequate. 

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