Frequently Asked Questions 

A biological safety cabinet (BSC) is a ventilated cabinet which uses a combination of HEPA filtration, laminar air flow and containment to provide personnel, product or environmental protection from biohazardous agents. This is accomplished by air intake and recirculation that is filtered prior to exhausting to the cabinet exterior. It is distinguished from a chemical fume hood by the presence of HEPA filtration and the laminar nature of the air flow. 

A laminar flow cabinet or laminar flow hood or tissue culture hood is a carefully enclosed bench designed to prevent contamination of semiconductor wafers, biological samples, or any particle sensitive device. Air is drawn through a High Efficiency Particulate Air (HEPA) filter and blown in a very smooth, laminar flow towards the user or towards the work surface. The cabinet is usually made of stainless steel with no gaps or joints where spores might collect. Laminar flow cabinets do not protect the user or the environment and cannot be used with infectious material. 

HEPA stands for High Efficiency Particulate Air filter and is capable of removing microscopic organisms with an efficiency of at least 99.97%. These filters help protect the user, the product in the workspace and the environment, but must be checked annually to ensure that they are functioning properly. 

A Clean room is defined by ISO14644-1 as "a room in which the concentration of airborne particles is controlled, and which is constructed and used in a manner to minimize the introduction, generation, and retention of particles inside the room and in which other relevant parameters, e.g. temperature, humidity, and pressure, are controlled as necessary." The design of clean room HVAC systems is a speciality area requiring the unique understanding of cleanliness guidelines, airflow, room pressurization, code requirements, speciality equipment, precise control, and many more details. 

• Only authorized personnel will be allowed inside the cleanroom.

• Only take what is necessary into the cleanroom.

• Only dedicated tools are allowed in the cleanroom.

• Gown in the prescribed manner over your non-frayed/non-ripped, low-linting clothes.

• Always make sure that all the head/facial hair is covered inside the cleanroom.

• When using an air shower, turn a minimum of three times around (slowly) during the ON cycle time.

• Keep doors from clean room to gowning area closed.

• Keep the cleanroom garments closed at all times while in the cleanroom.

• Use pass-through properly.

• Maintain good air flow management. "Product gets air first."

• Be discrete in coughing, sneezing, blowing your nose. If you can, go into the service area or gowning room. At the very least, turn away from the processing area and change your vinyl gloves before commencing processing again.

• People who have not been trained properly to meet the cleanroom usage requirements will not be allowed inside the cleanroom. The Cleanroom supervisor has the last word.

• No cosmetics, tobacco products, handkerchiefs, tissues, food products, drinks, wooden/mechanical pen/pencils, perfumes, colognes, watches, jewellery, cassette players, phones, beepers, combs, cardboard or non-cleanroom approved papers are allowed.

• No blueprints, operation manuals or instruction sheets are allowed.

• Do not bring any tools/ equipment into the cleanroom from the maintenance shop to work in the cleanroom.

• No bare clothes are allowed inside the cleanroom.

• Do not expose any facial/head hair.

• Do not open the door to the cleanroom until the ON cycle of the air shower is over.

• Do not open the door to the cleanroom for communication or passing of products back and forth – use the pass-through instead.

• Do not use pass-through for storage.

• Do not block the air flow from the filter to the product.

• Do not congregate. No running and try to maintain silence.

Contamination is a process or act that causes materials or surfaces to be soiled with contaminating substances. There are two broad categories of surface contaminants: film type and particulates. These contaminants can produce a “killer defect” in a miniature circuit. Film contaminants of only 10 nm (nanometers) can drastically reduce coating adhesion on a wafer or chip. It is widely accepted that particles of 0.5 microns or larger are the target. However, some industries are now targeting smaller particles. 

Latest ISO 14644 replaces FED Std 209E. 

There is no relationship at all. For example- a clean room with no one in it might be class 100, while the addition of personnel will send it into other higher categories. however, suppose the filters supplying a room were thoroughly checked for leaks, and all significant leaks were sealed, this room is operating at maximum efficiency with respect to the filters, and since the filters are mechanical in nature, there is nothing the operator can do to change conditions in this area.

The achievement of a particular class would relate to the number of air changes per hour as well as the scavenging design of the system.

Validation is the process of establishing documentary evidence demonstrating that a procedure, process, or activity carried out in testing and then production maintains the desired level of compliance at all stages. In the pharmaceutical industry, it is very important that in addition to final testing and compliance of products, it is also assured that the process will consistently produce the expected results. 

Air Changes per hour= CFM X 60 ÷ room volume = measuring with air capture hood

It states the maximum time interval between airborne particle concentration testing of a cleanroom of ISO class 5 and below is six months and ISO class 6 and above is 12 months.

Test Parameter                                                                                                      Class                                             Maximum Time Interval

Airborne particle concentrations                                                        = ISO Class 5                                                  6 months

Schedule of additional tests                                                                    >ISO Class 5                                                 12 months

Airflow velocities in unidirectional airflow                                   All classes                                                      6 months

Airflow volume supply in non-unidirectional airflow           All classes                                                     12 months

Pressure differentials                                                                                  All classes                                              Continuously monitored

Clean room maintained virtually free of contaminants, such as dust or bacteria, are used in laboratory work and in the production of precision parts for electronic or aerospace equipment. In the clean room standard ISO 14644-1 "Classification of Air Cleanliness" the classes are based on the formula:

Cn = 10N (0.1 / D)2.08    (1)

where Cn = maximum permitted number of particles per cubic meter equal to or greater than the specified particle size, rounded to whole number N = is the ISO class number, which must be a multiple of 0.1 and be 9 or less D = is the particle size in micrometers