NSF/ANSI49 standard secondary biosafety cabinet design and testing requirements

NSF/ANSI49 standard secondary biosafety cabinet design and testing requirements
NSF/ANSI49 is one of the most versatile international safety cabinet safety certifications in the world. The standards have detailed descriptions and requirements for safety cabinet performance grading and safety performance testing. In 2002, ANSI/NSF49 officially received official recognition from the American National Standards Institute (ANSI) and became the unified standard for US biosafety cabinets. This article focuses on the design and testing requirements of the NSF/ANSI49 standard secondary biosafety cabinet.
The biological safety cabinet is divided into I, II and III. Class I biosafety cabinets are suitable for testing samples or products that do not require protection; Class II biosafety cabinets are used to protect human, sample, and environmental operations, and are available in Types A1, A2, B1, and B2. Except for the A1 type, it is suitable for the operation of producing toxic chemicals or radioactive substances. Class II A biosafety cabinets feature no hard-tube exhaust ducts, 30% of HE2PA filtered gas is discharged into the laboratory, and 70% constitutes a portion of the vertical flow of the sample. The difference between A1 and A2 is that the A1 type biosafety cabinet allows the polluted air duct and the static pressure tank to be positive pressure and the A2 type is only allowed to be negative pressure. The HEPA filtered gas in the Class II B biosafety cabinet is discharged through the hard pipe. 30% of the B1 type biosafety cabinet exhaust gas can be recycled, and the B2 type is 100% full row. The Class III biosafety cabinet is a fully enclosed structure that is operated in the cabinet by rubber gloves attached thereto. The cabinet has a negative pressure of 120 Pa. The airflow entering the cabinet is filtered by HEPA and filtered by double HEPA before discharge. It is the highest specification biosafety cabinet.
All materials used in the manufacture of biosafety cabinets are required to be resistant to abrasion, corrosion, cracking, fire and moisture, non-toxic and odorless, and are made of materials that are reasonably stable and stable. When designing and manufacturing biosafety cabinets, safety considerations, protection of personnel, samples and environment should be considered, convenience and cleanliness, and good performance. For this purpose, 30 specific requirements for the design and construction of secondary biosafety cabinets are proposed, as shown in Table 1.
Table 1 Design and construction requirements for secondary biosafety cabinets
Design and construction
Claim
Cleaning ability
The internal working surface and exposed inner surface are easy to operate, easy to clean, and can be used to remove pollution.
Purification
The biosafety cabinet is designed to remove contamination with formaldehyde gas.
Overall design
Type A1: Allows a positive pressure contaminated air duct and static pressure tank;
Type A2/B1: All contaminated air ducts and static pressure tanks maintain negative pressure;
Type B2: All contaminated air ducts and static pressure tanks are held under negative pressure or enclosed in direct exhaust pipes that are not recirculated.
Inner apex and inner corner
The inner radius of the intersection of the second and third plates is at least 110°, the minimum radius of the intersection of the second plate (vertical or horizontal) is 3.2 mm, and the minimum radius of the intersection of the third plate is 6. 3 mm.
Outer apex and outer corner
The joint is closed, smooth, and has no sharp edges.
Joint and weld
All internal and external surface joints should be smooth and sealed.
Fastening method
Do not spray too much paint on all metal fasteners involved in repairs.
Weld
Meet the smooth requirements of the application surface.
solder
Used to seal large seams or as a fillet material.
Detachable panel
The safety cabinet is equipped with a detachable panel located in front of the blower, motor and filter inlet, designed to minimize openings and requires a complete seal.
stability
After the safety cabinet is placed, it should not be shaken or tilted and passed the stability test.
Placement and base
The bottom of the biosafety cabinet should fit snugly to the floor or base to ensure a clean space of 10 cm below.
Bracket
The legs and feet of the bracket should be designed with no external screw. The bottom has a minimum contact diameter of 19 mm and is made of a smooth material to prevent damage to the ground.
Firmware and frame
The reinforcements and frames embedded in the wall are easy to clean and do not hide harmful substances.
Fixed panel
When designing and manufacturing fixed panels, the protrusions and openings should be minimized.
Door and bezel
The plates and frames used in the cabinet should be completely closed. Whether single or double slabs and frames should minimize the accumulation of foreign matter. There is no slide at the bottom of the single-layer board; the hollow part of the double-layer board must be closed. There should be an audible alarm, which will alarm when the sliding window can lift the height beyond the specified level.
Skylight, opening
Designed to deflect water droplets, easy to clean, double-panel type sunroof should be fitted with a sleeve.
Guide rail and guide
The track required for movement should be structurally designed to be easy to clean.
filter
  
The downflow and exhaust gases must be filtered through a HEPA filter. The filter should meet IEST-RP-CC- in terms of material, construction and assembly.
For 001 Type C filters, the filter material must meet the M IL-F-51079B standard. HEPA filter leakage does not exceed 0.01%
  
Leak test by HEPA filter. When designing, consideration should be given to facilitating the installation, testing and sealing of the filter.
Seals and sealants
The gasket to be installed should be safe, sealed and secure, and the gasket exposed to the surface should be easy to clean and have no internal angle. The corner joint and the gasket of the hollow part are sealed. HEPA filters, safety cabinet joints, and gaskets for panels should have a sealed connection. The seal strength should be tested by the gasket seal strength. The structural strength of the joint or junction of the sealing strip is determined by the sealing strip.
Piston and socket
It should be easy to access, and the power outlet exposed on the internal work surface should have a waterproof cover or a closed switch with a closed pad.
Alarm system
The alarm should be given when the following conditions occur: the moving window can exceed the height; the exhaust fan stops working; the exhaust capacity changes.
Electrical components
There is a thermal protection device. At maximum load or high temperature, when the voltage reaches 115% of the nominal voltage, it will not trip; the degree of fan opening should meet the relevant requirements of this standard; all fans have safety controllers, which can adjust the speed to maintain airflow balance; provide circuit according to national electrical codes. Load protection, the single circuit is a 3-core cable, and the ground wire is connected to the rack. The motor or luminaire and socket are separately protected. Circuit overload protection is provided for all outlets, and the switch is mounted outside the work area. The circuit diagram is attached to the outside of the pressure exhaust system. Provide starting current operating power, circuit requirements. Replaceable electrical components are not permitted to be installed in a contaminated pressure exhaust system.
illumination
Lamps, rectifiers, and starters should not be installed in contaminated areas and should be easy to handle. The light intensity of the working surface complies with the requirements of 6.5 of this standard. It is not recommended to install UV lamps in the biosafety cabinet. If the buyer needs to install it, it will not lower the specified performance requirements.
Differential Pressure Gauge
The differential pressure gauge is installed according to the manufacturer's specifications. The hose connected to the differential pressure gauge and the sampling inlet are fastened with a positive pressure clamp. If the leak detection port has a threaded connection, 3 threaded connections must be made.
Drainage channels
A drain groove is provided below the work surface. Connect the drain pipe to it and install a ball valve of 0.94 cm or larger. Tubes and valves should meet the requirements. The drain tank has a volume of at least 4 L. The drain valve should have an identification label indicating whether it is on or off.
Diffuser placement
Removable components should be designed and manufactured to ensure they can be reinstalled in the correct working position.
Work area component placement
For detachable work surfaces, the intake and exhaust grilles are designed and constructed to ensure reinstallation in the correct working position.
Height and width
The safety cabinet should be able to pass through a 2 m × 0.9 m doorway.
Nameplate
There is a striking nameplate in front of the safety cabinet, including the following: manufacturer name, address; safety cabinet style, type, serial number; downward inward flow rate set point; downward flow rate test grid set point; inflow rate test method Potential pollution emissions are predicted; voltage requirements.
     
In addition to requiring manufacturers to design and manufacture safety cabinets according to standards, the NSF/ANSI49 standard also requires manufacturers to perform safety cabinet quality control tests. All detachable parts should be in place during the test, and all test results should meet the technical requirements listed in Table 2. The NSF/ANSI49 standard specifies the recent (within 1 year) calibration record and the 3-year quality control test results of the biosafety cabinet.
Table 2 Performance requirements for secondary biosafety cabinets
Test items
skills requirement
Pressure decay, soap bubble, tracer gas leak test
When the safety cabinet is operating normally, all gases discharged under positive pressure are not leaking. All seals should be leak-free by decompression or soap test.
Pressure reduction test: Pressurize the safety cabinet to 500 Pa, turn off the pressurized gas, and reduce the pressure by no more than 10% after 30 minutes.
Soap bubble test: no soap bubbles are produced at the joints, gaskets, etc. under the pressure of 500 Pa ±10%.
氦 Leak test: When the safety cabinet is pressurized to 500 Pa and the radon concentration is at least 15%, the leak measured at any place does not exceed 1 × 10 -5 cc / s.
Sulfur Hexafluoride (SF6) Leakage Test: When pressurized with SF6 to 500 Pa, the leak measured at any point should not exceed 5 × 10 -7 cc / s.
HEPA filter leak test
Detects the integrity and containment of HEPA filters, filter covers, filter-related equipment for downflow and gas discharge. When measured with a linear scale or a logarithmic scale photometer, the aerosol penetration at any point of the scanable filter shall not exceed 0.01% of the upstream gas concentration; the infiltration of the filter aerosol shall not exceed 0.005% of the upstream gas concentration.
Noise level test
The noise level is measured at nominal rate operation. Measured at 30 cm on the front of the cabinet and 38 cm above the vertical centerline above the work surface. When the maximum noise in the environment does not exceed 57 dbA, the noise at the measuring point of the safety cabinet should not exceed 67 dbA.
Illumination test
When the background light intensity is (110 ± 50) lx, the illumination intensity above the workbench is not less than 650 lx, and each count value is not less than 430 lx.
Vibration test
When operating at nominal wind speed, the center of the working surface vibrates at 10 Hz to 10 kHz, and the displacement of the object does not exceed 5 × 10 -6 m rms amplitude.
Personnel protection test
Personnel protection: The system should be subjected to (1~8) × 10 8 Bacillus subtilis for 5 min. The number of B. subtilis colonies growing on 6 samplers per test is no more than 10. After sampling for 30 minutes with a slit air sampler, no more than 5 B. subtilis colonies were tested each time. This test was repeated 3 times (the quality control plate used should be suitable for Bacillus subtilis growth).
Sample protection test
Sample protection: The system should be subjected to (1 ~ 8) × 10 6 Bacillus subtilis for 5 min. The number of bacteria growing on each test plate should not exceed 5, and the number of repeats should be repeated 3 times (the quality control plate should be suitable for Bacillus subtilis growth).
Cross-contamination protection test
Protection against cross-contamination: The system should withstand (1-8) × 10 4 B. subtilis for 5 min. Bacillus subtilis colonies must be grown on the plate within 36 cm of the attack surface as a positive control. The number of bacterial growth on the plate in the central region was not more than 2/times, and was repeated 3 times. Each test included the left and right sides of the biosafety cabinet.
Stability test
It is confirmed by experiments that the biological safety cabinet will not fall over and deform under a certain pressure, and the working surface is not offset when the load is heavy, and the load is not inclined. Anti-overturn: Meet the UL310121 standard. Anti-deformation: When static, the top edge and one side of the safety cabinet are subjected to 110 kg side force respectively, the top leading edge and one side move forward by no more than 1.6 mm. Work surface anti-offset: uniformly load 23 kg of test object in the area of ​​25 cm × 25 cm in the center of the working surface, and the working surface is not permanently deflected after removal. Anti-tilt: 110 kg of the test object is loaded on the front edge of the safety cabinet, and the bottom of the back is not more than 1.6 mm from the ground.
Downstream airflow speed
Balanced downflow airflow rate: Balanced downflow airflow safety cabinet, the flow rate of each measuring point and the average flow rate should not exceed ±20% or ±0.08 m/s. Unbalanced downflow rate: The rate at which the wind is individually tested at any point in the safety cabinet deviates from the average downwind by no more than ±20% or ±0.08 m/s. The difference between the flow rate and the average flow rate at each point in each specified area must be ±20% or ±0.08 m/s.
Operating port inward airflow
Type A1: Directly measure the inward airflow rate of the operating port to a minimum of 0.4 m/s; the minimum inflow per meter of work area is 76 m 3 /person.
speed
Types A2, B1 and B2: Directly measure the inward airflow rate of the operating port to a minimum of 0.5 m/s; the minimum airflow per 0.3 m wide working area should be 0.03 m 3 /s.
Smoke flow pattern
The smoke flow pattern is measured at the nominal wind speed, the airflow in the working area is downward, the airflow around the operation port is inward, there is no dead angle, no backflow, and no spillage outside the safety cabinet.
Drainage leak test
The drain tank should accommodate 4 L and there should be no leakage after 1 h.
Motor/fan performance test
When the safety cabinet is at the nominal wind speed, the fan speed is not adjusted. When the pressure drop of the new filter increases by 50%, the total exhaust air volume does not decrease by more than 10%.
Electrical Safety
Meets UL3101 1
Each secondary biosafety cabinet shall be field tested after installation and annually to evaluate whether the installed biosafety cabinet meets the design requirements of current standards. In addition, when replacing the HEPA filter, repairing the internal parts of the safety cabinet, and shifting the safety cabinet, it is necessary to re-test; for the operation of specific hazardous materials and overload operation of key parts, retesting should normally be considered.
references
1. Zhang Jingfeng et al. Introduction to Class II (Laminar Flow) Biosafety Cabinet Standard (NSF249 2002) (2005)
2. HU Liang-yong. Test and Analysis of the Integrity of High Efficiency Particulate Air Filter in Biological Safety Cabinets (2010)

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