Thursday, February 11, 2010


Indoor Air Quality and Ventilation

Indoor Air Quality (IAQ) is an increasingly important issue in the work environment. The study of indoor air quality and pollutant levels within office environments is a complex problem. The complexity of studying and measuring the quality of office environments arises from various factors including:
  • Office building floor plans are frequently changing to accommodate increasingly more employees and reorganization.
  • Office buildings frequently undergo building renovations such as installation of new carpet, modular office partitions and free-standing offices, and painting.
  • Many of the apparent health symptoms are vague and common to both the office and home environment.
  • Guidelines or standards for permissible personal exposure limits to pollutants within office buildings are very limited.

Many times odors are associated with chemical contaminants from inside or outside the office space, or from the building fabric. This is particularly noticeable following building renovation or installation of new carpeting. Out-gassing from such things as paints, adhesives, sealants, office furniture, carpeting, and vinyl wall coverings is the source of a variety of irritant compounds. In most cases, these chemical contaminants can be measured at levels above ambient (normal background) but far below any existing occupational evaluation criteria.

NIOSH has conducted hundreds of building studies which indicate that the most likely sources of this problem are - poor ventilation, poor thermal conditions, too high or low humidity, emissions from office machines, copiers and other building contaminants and poor ergonomic layout of workstations.

Overview of Ventilation Design

Relative Humidity Winter Temperature Range Summer Temperature Range
30% 68.5 - 76.0 F 74.0 - 80.0 F
40% 68.5 - 75.5 F 73.5 - 79.5 F
50% 68.5 - 74.5 F 73.0 - 79.0 F
60% 68.0 - 74.0 F 72.5 - 78.0 F
Note: Relative humidity above 50% is not recommended because it can promote mold growth.

Indoor Air Pollution

An inadequately ventilated office environment or a poorly designed ventilation system can lead to the build up of a variety of indoor air pollutants. Air pollutants can originate within the building or be drawn in from outdoors. Examples of sources that originate outside a building include:
  • pollen, dust and fungal spores
  • general vehicle exhaust
  • odors from dumpsters
  • re-entrained exhaust from the building itself or from neighboring buildings

Examples of sources that originate from within the building include:
  • building components and furnishings
  • smoking
  • maintenance or remodeling activities (painting, etc.)
  • housekeeping activities
  • unsanitary conditions (standing water from clogged drains or dry traps) and water damage
  • emissions from office equipment or special use areas (print shops, laboratories, or food preparation areas)

Controls to Prevent Indoor Air Pollution

The following recommendations and guidelines are useful in preventing indoor air quality problems:
  • HVAC systems should receive periodic cleaning and filters should be changed on a regular basis on all ventilation systems.
  • The ventilation system should introduce an adequate supply of fresh outside air into the office and capture and vent point air pollutant sources to the outside.
  • Office machinery should be operated in well-ventilated areas. Most office machinery does not require local exhaust ventilation in areas that are already provided with 7-10 air changes per hour. Photocopiers should be placed away from workstations. Workers should vary work tasks to avoid using machines excessively.
  • Office equipment should be cleaned/maintained according to the manufacturer's recommendations. Properly maintained equipment will not generate unhealthy levels of pollutants.
  • Special attention should be given to operations that may generate air contaminants (such as painting, pesticide spraying, and heavy cleaning). Provisions for adequate ventilation must be made during these operations or other procedures, such as performing work off-hours or removing employees from the immediate area, utilized.


Wednesday, February 10, 2010

Monoblock centrifugal pump

Monoblock centrifugal pumps are widely used in a variety of applications. In many applications the role of monoblock centrifugal pump is critical and condition monitoring is essential. Vibration based continuous monitoring and analysis using machine learning approaches are gaining momentum. Particularly artificial neural networks, fuzzy logic were employed for continuous monitoring and fault diagnosis. This paper presents the use of C4.5 decision tree algorithm for fault diagnosis through statistical feature extracted from vibration signals of good and faulty conditions.
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Smowtion ...
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