DETECTION OF MEDICAL DEFENSE AGAINST BIOLOGICAL MATERIALS

File: 123096_sep96_decls1_0094.txt
Page: 0094
Total Pages: 109

Subject: DETECTION OF MEDICAL DEFENSE AGAINST BIOLOGICAL MATERIALS       

Unit: OTSG        

Parent Organization: HSC         

Box  ID: BX003203

Folder Title: DETECTION OF MEDICAL DEFENSE AGAINST BIOLOGICAL MATERIALS                                       

Document Number:          1

Folder Seq  #:         21













                           organisms but are not as efficient in collecting particles in the size
                           range of greatest importance.   A special problem of liquid impingers is
                           the prevention of freezing in sampling operacions at very low
                           temperatures.  The liquid impingers most commonly used are of a
                           comparacively uniform design, usually of glass.   Common to all ordinary
                           samplers of this type is the rather low airflow capacity, mostly less
                           than 30 lilres per minute. Impingement into a liquid film is a recent
                           improvement. The applicatiorrof this principle has made possible a
                           dramatic increase in capacity, so that volumes of several thousand
                           litres per minute may be sampled (see also paragraph 606d,
                           electrostatic Precipitators).

                           b. Surface impactors - Particles are deposited directly on solid
                           surfaces which may be coated, or in the form of a solid nutrient
                           medium. The air inlets may have different shapes and arrangements, the
                           orifice having the shape of A SliL or a circle. In the case of
                           deposition of the particles on a dry surface, they are subsequently
                           washed into A liniiid for final collection.  In this case the -nitial
                           effect of dessic;tion may be important. All techniques involving
                           impaction on dry surfaces are deleterious to the viability of
                           vegetative organisms and are more suitable for,spores. A wide variety
                           of designs is in use; one of the roost widely used is the Andersen
                           sampler, a sieve type sampler which separates particles according to
                           size ranges. The particles are impacted directly on to agar medium in
                           Petri dishes, they may be incubated without further treatment. It
                           should be kept in mind that impaction procedures are not as a rule
                           applicable to virus sampling.

                           c. Filtration Samplers - Some samplers use a filter composed of minute
                           fibres (cellulose, asbestos, glasswool, etc.) which remove particles
                           from the air by absorptive and electrostatic forces. Others employ
                           membranes on which the particles are retained by sieving. As with
                           impaction on solid surfaces, it is necessary to transfer the collected
                           particles into a liquid, for example by washing. A new type of gelatin
                           filter simplifies this in chat the -whole filter is simply dissolved in
                           liquid. In the case of ordinary membrane filtration, the membrane
                           itself may be transferred directly on to a solid medium which serves as
                           a carrying surface for the growth of bacterial colonies. Except for
                           the so-called High Volume Air Sampler (capacity about 1500 litres of
                           air per minute) which employs a large sheet (about 20 x 25 cm) of
                           filter paper, filtration samplers have a restricted capacity of the
                           same order &a the liquid impingers. A dry fibrous system is more
                           suitable for the collection of spores. Due LO the fact that this
                           system requires the flow of air to be passing through, it may kill
                           vegetativ: cells.
                           d. Electrostatic Precipitators - In samplers of this type, the
for the particles is electrically charged. The air
                           may also be ionized, (and must be dried in order to avoid an electrical
                           arc) prior LO passing over the surface which may be solid (glass, agar)
                           or fluid. An important characteristic of samplers of this is their low
                           resistance to flow which permits high air flow rates* The newer types
                           represent a great improvematt and capacities of several thousand
                           litres of air per minute are now within reach. Work Continues to


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Document 109 f:/Week-36/BX003203/DETECTION OF MEDICAL DEFENSE AGAINST BIOLOGICAL MATERIALS/detection of medical defense against biological :1217960927452
Control Fields 17
File Room = sep96_declassified
File Cabinet = Week-36
Box ID = BX003203
Unit = OTSG
Parent Organization = HSC
Folder Title = DETECTION OF MEDICAL DEFENSE AGAINST BIOLOGICAL MATERIALS
Folder Seq # = 21
Subject = DETECTION OF MEDICAL DEFENSE AGAINST BIOLOGICAL
Document Seq # = 1
Document Date =
Scan Date =
Queued for Declassification = 01-JAN-1980
Short Term Referral = 01-JAN-1980
Long Term Referral = 01-JAN-1980
Permanent Referral = 01-JAN-1980
Non-Health Related Document = 01-JAN-1980
Declassified = 17-DEC-1996