Basic Documentation

Table Of Contents
Laboratory Ventilation Codes and Standards
Siemens Industry, Inc. 62
Topic Requirement(s) Commentary
Biosafety
Level 4
(Continued)
National Sanitation Foundation, NSF 49 -2008, Biosafety Cabinetry: Design,
Construction, Performance and Field Certification
3 Definitions
3.3. 4 Biosafety Level 4 Practices, safety equipment, and facility design and
construction are applicable for work with dangerous and exotic agents that have a
high individual risk of life-threatening disease, which may be transmitted via the
aerosol route and for which there is no available vaccine or therapy. Agents with a
close or identical antigenic relationship to Biosafety Level 4 agents also should be
handled at this level. When sufficient data are obtained, work with these agents may
continue at this level or at a lower level. Viruses such as Marburg or Congo-Crimean
hemorrhagic fever are manipulated at Biosafety Level 4.
The primary hazards to personnel working with Biosafety Level 4 agents are
respiratory exposure to infectious aerosols, mucous membrane or broken skin
exposure to infectious droplets, and autoinoculation. All manipulations of potentially
infectious diagnostic materials, isolates, and naturally or experimentally infected
animals pose a high risk of exposure and infection to laboratory personnel, the
community, and the environment.
The laboratory worker's complete isolation from aerosolized infectious materials is
accomplished primarily by working in a Class III BSC or in a full-body, air-supplied,
positive-pressure personnel suit. The Biosafety Level 4 facility itself is generally a
separate building or completely isolated zone with complex, specialized ventilation
requirements and waste management systems to prevent release of viable agents to
the environment.
A dedicated non-recirculating ventilation system is provided. Only laboratories with
the same HVAC requirements (i.e., other BSL-4 labs, ABSL-4, BSL-3-Ag labs) may
share ventilation systems if gas-tight dampers and HEPA filters isolate each
individual laboratory system.
The supply and exhaust components of the ventilation system must be designed to
maintain the laboratory at negative pressure to surrounding areas and provide
differential pressure or directional airflow, as appropriate, between adjacent areas
within the laboratory.
Redundant supply fans are recommended. Redundant exhaust fans are required.
Supply and exhaust fans must be interlocked to prevent positive pressurization of the
laboratory.
The ventilation system must be monitored and alarmed to indicate malfunction or
deviation from design parameters. A visual monitoring device must be installed near
the clean change room so proper differential pressures within the laboratory may be
verified prior to entry.
NSF essentially repeats the BSL definitions
from the BMBL.