Editing Biosafety level (section)

=== Biosafety level 4{{anchor|Level 4}} ===
{{See also|List of biosafety level 4 organisms}}
[[File:Positive-pressure biosafety suit.jpg|right|thumb|CDC technician dons an older-model positive-pressure suit before entering one of the CDC's earlier BSL-4 labs.]]

Biosafety level 4 (BSL-4) is the highest level of biosafety precautions, and is appropriate for work with agents that could easily be aerosol-transmitted within the laboratory and cause severe to fatal disease in humans for which there are no available vaccines or treatments. BSL-4 labs are generally set up to be either cabinet laboratories or protective-suit laboratories.<ref name=":0" /> In cabinet laboratories, all work must be done within a [[Biosafety cabinet#Class III|class III biosafety cabinet]]. Materials leaving the cabinet must be decontaminated by passing through an [[autoclave]] or a tank of [[disinfectant]]. The cabinets themselves are required to have seamless edges to allow easy cleaning. Also, the cabinet and all materials within must be free of sharp edges to reduce the risk of damage to the gloves. In a protective-suit lab, all work must be done in a [[Biosafety cabinet#Class II|class II biosafety cabinet]] by personnel wearing a [[positive pressure personnel suit|positive pressure suit]]. To exit a BSL-4 lab, personnel must pass through a chemical shower for decontamination, then a room for removing the positive-pressure suit, followed by a personal shower. Entry into the BSL-4 lab is restricted to trained and authorized individuals, and all persons entering and exiting the lab must be recorded.<ref name=CDCBiosafety/>

As with BSL-3 laboratories, BSL-4 labs must be separated from areas that receive unrestricted traffic. Also, airflow is tightly controlled to ensure that air always flows from "clean" areas of the lab to areas where work with infectious agents is being performed. The entrance to the BSL-4 lab must also employ [[airlock]]s to minimize the possibility that aerosols from the lab could be removed from the lab. All laboratory waste, including filtered air, water, and trash must also be decontaminated before it can leave the facility.<ref name=CDCBiosafety/>

Biosafety level 4 laboratories are used for diagnostic work and research on easily transmitted pathogens which can cause fatal disease. These include a number of viruses known to cause [[viral hemorrhagic fever]] such as [[Marburg virus]], [[Ebola virus]], [[Lassa virus]], and [[Crimean-Congo hemorrhagic fever]]. Other pathogens handled at BSL-4 include [[Hendra virus]], [[Nipah virus]], and some [[flavivirus]]es. Also, poorly characterized pathogens which appear closely related to dangerous pathogens are often handled at this level until enough data is obtained either to confirm continued work at this level, or to permit working with them at a lower level.<ref name=BMBLRecs/> This level is also used for work with [[smallpox]] virus, though this work is only performed at the [[Centers for Disease Control and Prevention]] in Atlanta, United States, and the [[State Research Center of Virology and Biotechnology]] in Koltsovo, Russia.<ref name=BMBLSmallpox>{{cite book |title=Biosafety in Microbiological and Biomedical Laboratories, 5th ed. |publisher=U.S. Department of Health and Human Services |date=December 2009 |url=https://www.cdc.gov/biosafety/publications/bmbl5/bmbl5_sect_viii.pdf |section=Section VIII-Agent Summary Statements |page=219 |access-date=4 May 2016 |url-status=live |archive-url=https://web.archive.org/web/20160513215241/http://www.cdc.gov/biosafety/publications/bmbl5/bmbl5_sect_viii.pdf |archive-date=13 May 2016 }}</ref>

<gallery heights="125" widths="200">
File:NIAID Integrated Research Facility - Positive Pressure Personnel Suit Inspection.jpg|Regular inspection of positive-pressure suits to locate any leaks<ref>{{cite news|last1=Seligson|first1=Susan|title=Video Offers Glimpse of Biosafety Level 4 Lab Science webcast "threads the NEIDL"|url=http://www.bu.edu/today/2013/video-offers-glimpse-of-biosafety-level-4-lab/|newspaper=Boston University|access-date=5 December 2014|date=7 March 2013|url-status=live|archive-url=https://web.archive.org/web/20141210184637/http://www.bu.edu/today/2013/video-offers-glimpse-of-biosafety-level-4-lab/|archive-date=10 December 2014}}</ref>
File:NIAID Integrated Research Facility - SPECT.jpg|alt=SPECT machine at BSL-4 imaging facility that separates subjects with pathogens from the machines.|[[SPECT]] machine at BSL-4 imaging facility that separates subjects with [[pathogen]]s from the machines<ref name=irf/>
File:NIAID Integrated Research Facility - MRI.jpg|The circular containment tube separates the patient table in the "hot" zone (pathogen present) from the "cold" zone around this [[MRI]] machine.
File:NIAID Integrated Research Facility - Air Pressure Resistant (APR) door.jpg|Air pressure resistant (APR) door to separate the hot and cold zones
File:NIAID Integrated Research Facility - Positive Pressure Personnel Suit.jpg|Working inside a BSL-4 lab with air hoses providing positive air pressure
File:NIAID Integrated Research Facility - Class III Biosafety Cabinet.jpg|Inside a Class III biological safety cabinet with an [[Bioaerosol|aerosol]] control platform
File:Effluent decontamination system.jpg|[[Effluent decontamination system]] of a BSL-4 lab of [[NIAID]]
</gallery>

==== BSL-4 facilities for extraterrestrial samples ====
{{Main|Extraterrestrial sample curation}}
[[Sample-return mission]]s that bring samples from a [[Planetary protection#Category V|Category V]] body back to Earth must be curated at facilities rated BSL-4. Because the existing BSL-4 facilities in the world do not provide the level of cleanliness needed for such pristine samples,<ref name="Hsu 2009">{{Cite web |last=Hsu |first=Hsu |date=2009-12-03 |title=How to Protect Mars Samples on Earth |url=https://www.space.com/7625-protect-mars-samples-earth.html |access-date=2024-12-19 |website=Space.com |language=en}}</ref> there is a need to design a facility dedicated to curation of restricted (potentially [[biohazard]]ous) [[extraterrestrial materials]]. The systems of such facilities must be able to contain unknown biohazards, as the size of any putative alien [[microorganism]] is unknown. Ideally, it should filter particles down to 10 [[nanometer]]s, and release of a particle 50 nanometers or larger is unacceptable under any circumstance.<ref name="GTA 2013">{{Cite web|url=https://science.nasa.gov/media/medialibrary/2013/01/17/ESF_Mars_Sample_Return_backward_contamination_study.pdf|archiveurl=https://web.archive.org/web/20160602150139/http://science.nasa.gov/media/medialibrary/2013/01/17/ESF_Mars_Sample_Return_backward_contamination_study.pdf|url-status=dead|title=European Science Foundation – Mars Sample Return backward contamination – Strategic advice and requirements|archivedate=2 June 2016}}</ref>

Because NASA and ESA are collaborating on the Mars Sample Return campaign, due to return samples from [[Mars]] in the early 2030s, the need for a Sample Receiving Facility (SRF) is becoming more pressing. An SRF is expected to take 7 to 10 years from design to completion,<ref name="Assessment 2009">{{cite report|title=Assessment of Planetary Protection Requirements for Mars Sample Return Missions|publisher=National Research Council|page=59|year=2009|chapter=7: "Sample-Receiving Facility and Program Oversight"|chapter-url=http://www.nap.edu/openbook.php?record_id=12576&page=59}}</ref><ref name="MSRtaskgroup">{{Cite web |url=http://planetaryprotection.nasa.gov/summary/msr |title=Mars Sample Return: Issues and Recommendations (Planetary Protection Office Summary) |work=Task Group on Issues in Sample Return. National Academies Press, Washington, DC, 1997|archive-url=https://web.archive.org/web/20111015062937/http://planetaryprotection.nasa.gov/summary/msr |archive-date=15 October 2011 }}</ref> and an additional two years is recommended for the staff to become proficient and accustomed to the facilities.<ref name='Assessment 2009'/>