NATIONAL BUREAU OF STANDARDS REPORT

t

8056

This repo(.tiaas,.bmi

for information- and record,

purposes and is not to be reference*:

in- any publication.4

PREPARATION, SAMPLING AND ANALYSIS

OF COMBUSTION PRODUCTS

OF AIRCRAFT FINISH MATERIALS

By

J.J. Loftus, E. E. Hughes, D. Gross, A.F. Robertson

U. S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS

/
THE NATIONAL BUREAU OF STANDARDS

Functions and Activities

The functions of the National Bureau of Standards are set forth in the Act of Congress,

March 3, 1901, as amended by Congress in Public Law 619, 1950. These include the development and maintenance of the national standards of measurement and. the provision of means

and methods for making measurements consistent with these standards; the determination of

physical constants and properties of materials; the development of methods and instruments

for testing materials, devices, and structures; advisory services to government agencies on

scientific and technical problems; invention and development of devices to serve special needs

of the Government; and the development of standard practices, codes, and specifications. The

work includes basic and applied research, development, engineering, instrumentation, testing,

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The scope of activities is suggested by the listing of divisions and sections on the inside of

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A complete listing of the Bureau’s publications can be found in National Bureau of Standards Circular 460, Publications of the National Bureau of Standards, 1901 to June 1947 ($1.25),

and the Supplement to National Bureau of Standards Circular 460, July 1947 to June 1957

($1.50), and Miscellaneous Publication 240, July 1957 to June 1960 (includes Titles of Papers

Published in Outside Journals 1950 to 1959) ($2.25); available from the Superintendent of

Documents, Government Printing Office, Washington 25, D.C.
NATIONAL BUREAU OF STANDARDS REPORT

NBS PROJECT NBS REPORT

1002-30-10627 August 2, 1963 8056

PREPARATION, SAMPLING AND ANALYSIS

OF COMBUSTION PRODUCTS

OF AIRCRAFT FINISH MATERIALS

ty

J. J. Loftus, E. E. Hughes, D. Gross* A. F. Robertson

for

Federal Aviation Agency

under

Agreement Number

FANAF-AP-23 of 3/25/63

Project 3 II-3XI

IMPORTANT NOTICE NATIONAL BUREAU OF

for use within the Governmer

and review. For this reason, whole or in part, is not aut Bureau of Standards, Washii

the Report has been specifics

Approved for public release by the

Director of the National Institute of

Standards and Technology (NIST)

on October 9, 2015.

'gress accounting documents intended

I is subjected to additional evaluation

:ure listing of this Report, either in the Office of the Director, National by the Government agency for which

i\ copies for its own use.

U. S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS
.
PREPARATION, SAMPLING AND ANALYSIS

OF COMBUSTION PRODUCTS

OF AIRCRAFT FINISH MATERIALS

BY

J.J. Loftus, E.E. Hughes, D. Gross, A.F. Rohertson

ABSTRACT

This report describes three techniques which

were used in burning samples of aircraft finish

materials with the objective of analysis of the

resulting decomposition products. In spite of

the fact that the methods differed significantly? varying from pyrolysis in a closed vessel to

burning in the open, and the fact that the techniques of sampling were varied with the objective

of offsetting adsorption problems, the results of

mass spectrometric analysis of the products were

not greatly different. No halogen compounds were

detected in the vinyls known to contain them. It.

was concluded that the methods used were inadequate to provide detailed information on the composition of the gases released during burning of

the materials tested.

1. INTRODUCTION

In connection with a study of methods for more adequately

limiting the flammability of aircraft interior finish and construction materials an attempt was made to identify and measure

the concentration of decomposition products. Schriesheim (1)

had previously made somewhat similar studies by pyrolyzing specimens at temperatures between 250 and 550°C in a closed vessel

and analyzing most of the combustion products by means of a

mass spectrometer. In his experiments the oxygen concentration

in the combustion products was frequently reduced below the five

percent level. Since active burning of materials in a self

supporting manner appears unlikely under such conditions it was

theorized that the decomposition products resulting from pyrolysis experiments of this type might not be most representative

of those likely to result from actual fire situations. Because

of this three different methods of producing the decomposition

products were used. The plan was to observe the influence of

varying degrees of confinement of specimen during burning on

the pyrolysis products.
2

The work was undertaken as an analytical or test study

lather than as a research investigation. This report describes

the sampling techniques used and reports on the results of the

analysis

2. EXPERIMENTAL EQUIPMENT AND METHOD

Three degrees of confinement of burning situations were

explored”

1. Pyrolysis in a closed though not gas tight heated tube

furnace as described in ASTM E 136-59T (2) at 550°C (s)

2. Combustion of the specimen by direct flame impingement

in a closed combustion chamber. (B)

3* Collection of a gas sample during burning of the specimen in the radiant panel flame spread test Int. Fed.

Std. 00136b (RP)

The equipment and experimental procedure used with each of these

will be described in turn.

2.1 Heated Tube Furnace

Samples of the combustion gases were collected during the

burning of the test materials in an available, electricallyheated tube, furnace (2) . Some modifications were made to the

furnace to adapt it for this purpose. The principal change was

the removal of the inner concentric refractory tube to allow for

a tube diameter opening of b inches, large enough to accomodate

a sampling test assembly. This assembly was made up of a removable furnace lid 5 1/2 inches in diameter which served to support

a wire mesh specimen basket at a depth of 6 inches into the tube

furnace, and a ST 12/30 taper joint fused to a 1/2 inch I.D.

pyrex tube. This tube was positioned to extend a depth of 2 1/2

inches into the furnace and a distance of 3 l/1* inches above the

wire basket. For observation purposes the lid was provided with

a 1 inch diameter opening, fitted with a mica window.

Figure ( 3 ) shows the complete gas sampling assembly used

with the furnace. A 100 mm gas drying tube with ST 12/30 pyrex

taper joints attached at both stop cock side arms was used to

collect samples for transfer to the mass spectrometer for analysis.

One arm was fitted into the ST 12/30 pyrex taper joint in the furnace lid and the other connected by rubber tubing to a 250 ml

Lrlenmeyer filtering flask. A three way stopcock, a mercury manometer and a vacuum pump completed the sampling apparatus.
- 3

- The furnace was preheated and set to maintain a temperature

of 550°C as indicated by a thermocouple located near the center

of the furnace. This temperature was sufficiently high to ignite

all specimens within 5 minutes and was selected to duplicate a

temperature condition used by Schriesheim (1) . No air flow was

supplied to the furnace.

With the lower stopcock open and the upper closed on the

sampling tube the entire sampling system was evacuated through

the 250 ml Erlenmeyer flask under a vacuum measured by a displacement of about 13-5 inches of mercury of the manometer. A

0.5 gram specimen of the material to be tested was placed in the

wire mesh basket and the furnace lid positioned snugly over the

furnace opening. Upon the ignition of the test material (usually

within 2 minutes) as evidenced by a burst of flame and the evolution of smoke, the gas tube stopcocks were opejqed and closed in

a single rapid motion during which time a sufficient gas sample

was collected in the sampling tube under vacuum.

2.2 Closed Combustion Chamber

This device shown in Figure (l) comprised a completely

closed system within which the specimen could be burned. Its

main features included the combustion chamber, ignition burner,

adjustable specimen holder^ air and gas metering equipment and

the gas sampling tube. In use, air and gas f hows, weie adjusted

to a level found to produce stable combustion conditions (O.OO3

- 0.004 cu ft/min gas and 0.2 cu ft/min air). The burner was lit

and a one half gram sample of the specimen was placed in a silica

dish on the sample support and the equipment assembled with the

sample tube cocks open.

The specimen was then raised into a position so that the

burner flame, which was about 1 1/4 inches in length, impinged

on it serving to ignite it. The burner was fastened in this

position and gases were allowed to continually escape through

the sampling tube. After operation in this manner for about 10

minutes and before flaming from the specimen had stopped, the

outer cock and then the inner cock of the sampling tube were

closed.

This method of burning the specimen and collected gas samples was used with the hope that the interior surfaces of the

equipment and sampling tube might become saturated and thips some

of the gas products otherwise likely to be adsorbed on the walls

might still remain in the gas or vapor phase.
2.3 Radiant Panel Gas Samples

The radiant panel flame spread test method (3) was modified

hy insertion of the gas sampling equipment shown in Figure (2)

in the air suction line used for collecting smoke samples. With

the objective of reducing adsorption difficulties expected with

organic type hose, the line between the smoke sample holder and

the sampling tube was replaced with stainless steel tubing.

The cocks were adjusted to permit bypassing the sampling tube

and the test was run in this way until the flames reached the nine

inch position or maximum smoke evolution rate had been achieved.

The cocks were then adjusted to pass the gas through the sampling

tube for the time period during which specimen flaming continued.

This ranged from 0.6 min to over 2 minutes and the cocks were then

again adjusted to permit bypassing the tube.

This technique was intended to provide a gas sample representative of those likely to be produced in open fires where considerable dilution with fresh air was likely*

3. Results

Two series of experiments were performed. In the first series

three materials, selected to represent a wide range of combustion

products, and a blank were tested by each of the combustion methods

previously described. The materials tested were a cotton fabric,

a vinyl floor covering incorporating a foamed rubber pad, and a

drapery material fabricated with cotton, mohair, and viscose fibers

together with a metal foil. These were designated as specimens 1,

25, and bl respectively.

These samples were first analyzed with the mass spectrograph

directly without pretreatment (i.e. concentration). The analysis,

Table 1, showed that only the components of air with increased

carbon dioxide, and some carbon monoxide and in one case hydrogen

were present. There was evidence of other compounds but their

concentration was so low they could not be identified. ' An attempt

was then made to concentrate the unidentified portion of several

samples. The samples were cooled with liquid nitrogen, the air

and other noncondensibles were pumped away and a spectrum was obtained of the residue after volatilization. Since water and carbon dioxide constituted the greater part of the condensible portion it was impossible to determine the presence of anything else

without first removing them. The volatilized residue was then

treated with a drying agent to remove water and with Ascarite to

remove the carbon dioxide. The remaining sample after this treatment was too minute to allow identification of any compounds.

Furthermore, the treatment prevented any estimate of the quantity

of the unidentified compounds.
- 5 - In general, the results for 0^, CO, and CCK seem to indicate that the excess air increased irom S to B zo RP. This is

to be expected, although the absence of this trend for Specimen

No. 4l could not be explained unless an error occurred in either

labeling the specimens or reporting the data. The rather unusual

analysis reported under BLANK (RP) probably can be attributed to

the fact that the combustion products of the radiant panel diluted

with fresh air were being analyzed. The complete absence of any

indication of halogens in specimen No. 25 for any of the sampling

methods suggests that either the concentration was below the sensitivity of the spectrometer used or the sampling and transfer

techniques were inadequate.

Because of the large quantities of air present in the samples

it was decided to use the Heated Tube furnace for the next group

of tests, with the objective of increasing concentration of decomposition products. In addition, no extraneous combustion products would be introduced in an electrically-heated furnace.

This was done and the l4 specimens shown in Table 2 were pyrolyzed

by this method. The one marked BLANK was a sample obtained from

the heated furnace but without introducing any specimen. The

samples were analyzed without treatment and the mass spectra obtained, Table 2, represented the entire gaseous phase in the sample tubes.

The major portion of each sample consisted of air, carbon

dioxide, carbon monoxide, nitrogen in excess of that in air and

argon in excess of that in air. The latter components are the

result of the depletion of oxygen in part of the air due to the

combustion process. In every case the above named components

constituted 98% or more of the sample, with the remainder consisting of a complex mixture of organic compounds. The value in

the column headed unidentified fraction is the percentage of the - total ion currents at all mass numbers, which would not be ascribed

to the identified compounds. It is not the actual concentration

of the unidentified fraction but is probably within one order of

magnitude of the actual concentration.

The mass numbers which contributed the major portion of the

ion currents at the unidentified masses are those which represent

ion fragments of unsaturated hydrocarbons containing from one to

three carbon atoms. Some of the large remainders arise from

pattern variation and other errors involved in the calculation

of the identified portion. There is also evidence of the presence

of aromatic compounds, principally benzene, at a concentration of

about 2-5% of the unidentified fraction.
- 6 - Because of the apparent inability of the mass spectrometer

to detect halogens from materials including those containing

poly (vinyl chloride) under the conditions of testing and sampling

used, the very sensitive qualitative Beilstein test for halogens

was performed on small samples of most of the specimens listed in

Table 2. Table 3 shows the results of application of this test

method. In addition, moist litmus paper was held in the smoke

produced during performance of the Beilstein test, and it was

found that with the single exception of specimen Bo. 4 all specimens produced an acid indication. Specimen 4 produced a basic

indication while specimen 75 showed initial acid and then basic

indication.

4. DISCUSSION

There are problems associated with the collection and transfer of combustion gases for analysis by the mass spectrometer,

which probably accounts for the lack of indication of certain

toxic components which are presumably present. Although the products analyzed in producing Table 2 were collected using a closed

system, maintained at high temperature, with no air supplied,

equally severe conditions might occur during fires in aircraft

compartments.

It was considered possible that certain compounds (Clp, HC1,

and oxides of nitrogen) which were not found in the gaseous phase

may have been adsorbed on solid carbon particles or in tar aerosols

However, no analyses were made of the liquid (including tar) portions of the samples (some of which were colored) since it seemed

that the information obtained would not justify the effort. It

may be noted that during analysis of the vacuum pyrolysis of

cellulose (4) the tar fraction was analyzed by prior heating in

a furnace opening directly into the mass spectrometer ionization

chamber. Other research studies employing gas chromatography (5*6)

have also found it desirable or necessary to carry the combustion

products directly into the analyzer without collection and handling

Since such techniques are apparently necessary, it may not

be profitable to consider the bottle collection of combustion

gases from full scale field studies. Where direct analysis instruments (e.g. of the infrared absorption type for CO and COp and the

magnetic susceptibility type for Op) are available for field use,

their use is recommended. Care should be taken to keep the length

of the sampling lines as short as possible. The use of colorimetric gas detecting tubes (7*8) for analysis of known or suspected

toxic gases should be considered. Such tubes should also be

placed as close as possible to the area being monitored to reduce

the amount of adsorption along the surfaces of sampling tubes.
- 7 -

It has been suggested that for the majority of fires and

almost irrespective of the type of lining materials used, the

principal toxic product would be carbon monoxide and that even

if more lethal gases were produced, the volume of CO would be

sufficiently great for it to constitute the major hazard. However,

the lack of adequate information on the synergistic toxic effects

of CO and very small quantities of other toxic products makes a

complete analysis of combustion products highly desirable.
- 8 -

5. REFERENCES

(1) Schriesheim, A., "Method for the Controlled Burning of

Comhustihle Materials and Analyses of the Combustion Gases"

BBS J. Research 5Z, 245-9 (1956).

(2) "Tentative Method of Test for Determining Noncombustibility

of Elementary Materials" (E 136-59T), 1959 Supplement to

Book of ASTM Standards, Part 5 ? 177.

(3) a. Int. Fed. Std. 00136b, Dec. 26, 1962.

b. Robertson, A.F. , Gross, D. and Loftus, J.JV, "A Method

for Measuring Surface Flammability of Materials Using

A Radiant Energy Source," ASTM Proc. 56* (1956).

(4) Madorsky, S.L., Hart, V.E. and Straus, S. "Pyrolysis of

Cellulose in a Vacuum", BBS J. Research 56, 343 “54, (1956).

(5) Martin, S.B. and Ramstad, R.W. "Compact Two-Stage Gas

Chromatograph for Flash Pyrolysis Studies" Anal. Chem. 33.

982-5 (1961).

(6) Sandler, S. and Beech, J.A. "Quantitative Analysis of Combustion Products by Gas Chromatography" Can. J. Chem. 38 . 1455-66 (I960).

(7) Kusnetz, H.L. "Evaluation of Direct Reading Colorimetric

Gas Detecting Devices", Final Report to Bu Ships, Public

Health Service, (1962).

(8) U.S. Testing Co. Report No. 83413, "Procedures and Analytical Methods for Determining Toxic Gases Produced by Synthetic

Materials", BuShips Contract N0bs-848l4 (1962).

(9) Coleman, E.H. "Gaseous Combustion Products from Plastics"

Plastics, 24, 416-418 (1959).
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TABLE 3

List of Materials as Classified by Beilstein Test

Materials showing negative indication (no halogen)

1, 11, 16, 65, 82, 88

Materials showing positive indication (halogen present)

21, 22, 2k, 28, 29, 31, 34, 35,

51, 52, 53, 58, 59, 60, 61, 62,

63, 66, 69, 70, 7k, 75, 85, 86, 87

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FURNACE

U. S. DEPARTMENT OF COMMERCE

Luther H. Hodges, Secretary

NATIONAL BUREAU OF STANDARDS

A. V. Astin, Director THE NATIONAL BUREAU OF STANDARDS

The scope of activities of the National Bureau of Standards at its major laboratories in Washington, D.C.,and

Boulder, Colorado, is suggested in the following listing of the divisions and sections engaged in technical work.

In general, each section carries out specialized research, development, and engineering in the field indicated by

its title. A brief description of the activities, and of the resultant publications, appears on the inside of the

front cover. WASHINGTON, D. C.

Electricity. Resistance and Reactance. Electrochemistry. Electrical Instruments. Magnetic Measurements.

Dielectrics. High Voltage. Absolute Electrical Measurements.

Metrology. Photometry and Colorimetry. Refractometry. Photographic Research. Length. Engineering Metrology.

Mass and Volume.

Heat. Temperature Physics. Heat Measurements. Cryogenic Physics. Equation of State. Statistical Physics.

Radiation Physics. X-ray. Radioactivity. Radiation Theory. High Energy Radiation. Radiological Equipment.

Nucleonic Instrumentation. Neutron Physics.

Analytical and Inorganic Chemistry. Pure Substances. Spectrochemistry. Solution Chemistry. Standard Refer- ence Materials. Applied Analytical Research. Crystal Chemistry.

Mechanics. Sound. Pressure and Vacuum. Fluid Mechanics. Engineering Mechanics. Rheology. Combustion

Controls.

Polymers. Macromolecules: Synthesis and Structure. Polymer Chemistry. PolymeF Physics. Polymer Characterization. Polymer Evaluation and Testing. Applied Polymer Standards and Research. Dental Research.

Metallurgy. Engineering Metallurgy. Metal Reactions. Metal Physics. Electrolysis and Metal Deposition.

Inorganic Solids. Engineering Ceramics. Glass. Solid State Chemistry. Crystal Growth. Physical Properties.

Crystallography.

Building Research. Structural Engineering. Fire Research. Mechanical Systems. Organic Building Materials.

Codes and Safety Standards. Heat Transfer. Inorganic Building Materials. Metallic Building Materials.

Applied Mathematics. Numerical Analysis. Computation. Statistical Engineering. Mathematical Physics. Operations Research.

Data Processing Systems. Components and Techniques. Computer Technology. Measurements Automation.

Engineering Applications. Systems Analysis.

Atomic Physics. Spectroscopy. Infrared Spectroscopy. Far Ultraviolet Physics. Solid State Physics. Electron

Physics. Atomic Physics. Plasma Spectroscopy.

Instrumentation. Engineering Electronics. Electron Devices. Electronic Instrumentation. Mechanical Instru- ments. Basic Instrumentation.

Physical Chemistry. Thermochemistry. Surface Chemistry. Organic Chemistry. Molecular Spectroscopy. Ele- mentary Processes. Mass Spectrometry. Photochemistry and Radiation Chemistry.

Office of Weights and Measures. BOULDER, COLO.

CRYOGENIC ENGINEERING LABORATORY

Cryogenic Processes. Cryogenic Properties of Solids. Cryogenic Technical Services. Properties of Cryogenic

Fluids.

CENTRAL RADIO PROPAGATION LABORATORY

Ionosphere Research and Propagation. Low Frequency and Very Low Frequency Research. Ionosphere Research. Prediction Services. Sun- Earth Relationships. Field Engineering. Radio Warning Services. Vertical

Soundings Research.

Troposphere and Space Telecommunications. Data Reduction Instrumentation. Radio Noise. Tropospheric

Measurements. Tropospheric Analysis. Spectrum Utilization Research. Radio-Meteorology. Lower Atmosphere

Physics.

Radio Systems. Applied Electromagnetic Theory. High Frequency and Very High Frequency Research. Fre- quency Utilization. Modulation Research. Antenna Research. Radiodetermination.

Upper Atmosphere and Space Physics. Upper Atmosphere and Plasma Physics. High Latitude Ionosphere

Physics. Ionosphere and Exosphere Scatter. Airglow and Aurora. Ionospheric Radio Astronomy.

RADIO STANDARDS LABORATORY

Radio Standards Physics. Frequency and Time Disseminations. Radio and Microwave Materials. Atomic Fre- quency and Time-Interval Standards. Radio Plasma. Microwave Physics.

Radio Standards Engineering. High Frequency Electrical Standards. High Frequency Calibration Services. High

Frequency Impedance Standards. Microwave Calibration Services. Microwave Circuit Standards. Low Frequency

Calibration Services.

Joint Institute for Laboratory Astrophysics- NBS Group (Univ. of Colo.).

USCOMM-NBS— OC

U. S. DEPARTMENT OF COMMERCE

Luther H. Hodges, Secretary

NATIONAL BUREAU OF STANDARDS

A. V. Astin, Director THE NATIONAL BUREAU OF STANDARDS

The scope of activities of the National Bureau of Standards at its major laboratories in Washington, D.C.,and

Boulder, Colorado, is suggested in the following listing of the divisions and sections engaged in technical work.

In general, each section carries out specialized research, development, and engineering in the field indicated by

its title. A brief description of the activities, and of the resultant publications, appears on the inside of the

front cover. WASHINGTON, D.C.

Electricity. Resistance and Reactance. Electrochemistry. Electrical Instruments. Magnetic Measurements.

Dielectrics. High Voltage. Absolute Electrical Measurements.

Metrology. Photometry and Colorimetry. Refractometry. Photographic Research. Length. Engineering Metrology.

Mass and Volume.

Heat. Temperature Physics. Heat Measurements. Cryogenic Physics. Equation of State. Statistical Physics.

Radiation Physics. X-ray. Radioactivity. Radiation Theory. High Energy Radiation. Radiological Equipment.

Nucleonic Instrumentation. Neutron Physics.

Analytical and Inorganic Chemistry. Pure Substances. Spectrochemistry. Solution Chemistry. Standard Refer- ence Materials. Applied Analytical Research. Crystal Chemistry.

Mechanics. Sound. Pressure and Vacuum. Fluid Mechanics. Engineering Mechanics. Rheology. Combustion

Controls.

Polymers. Macromolecules: Synthesis and Structure. Polymer Chemistry. PolymeF Physics. Polymer Characterization. Polymer Evaluation and Testing. Applied Polymer Standards and Research. Dental Research.

Metallurgy. Engineering Metallurgy. Metal Reactions. Metal Physics. Electrolysis and Metal Deposition.

Inorganic Solids. Engineering Ceramics. Glass. Solid State Chemistry. Crystal Growth. Physical Properties.

Crystallography.

Building Research. Structural Engineering. Fire Research. Mechanical Systems. Organic Building Materials.

Codes and Safety Standards. Heat Transfer. Inorganic Building Materials. Metallic Building Materials.

Applied Mathematics. Numerical Analysis. Computation. Statistical Engineering. Mathematical Physics. Operations Research.

Data Processing Systems. Components and Techniques. Computer Technology. Measurements Automation.

Engineering Applications. Systems Analysis.

Atomic Physics. Spectroscopy. Infrared Spectroscopy. Far Ultraviolet Physics. Solid State Physics. Electron

Physics. Atomic Physics. Plasma Spectroscopy.

Instrumentation. Engineering Electronics. Electron Devices. Electronic Instrumentation. Mechanical Instru- ments. Basic Instrumentation.

Physical Chemistry. Thermochemistry. Surface Chemistry. Organic Chemistry. Molecular Spectroscopy. Elementary Processes. Mass Spectrometry. Photochemistry and Radiation Chemistry.

Office of Weights and Measures. BOULDER, COLO.

CRYOGENIC ENGINEERING LABORATORY

Cryogenic Processes. Cryogenic Properties of Solids. Cryogenic Technical Services. Properties of Cryogenic

Fluids.

CENTRAL RADIO PROPAGATION LABORATORY

Ionosphere Research and Propagation. Low Frequency and Very Low Frequency Research. Ionosphere Research. Prediction Services. Sun- Earth Relationships. Field Engineering. Radio Warning Services, Vertical

Soundings Research.

Troposphere and Space Telecommunications. Data Reduction Instrumentation. Radio Noise. Tropospheric

Measurements. Tropospheric Analysis. Spectrum Utilization Research. Radio-Meteorology. Lower Atmosphere

Physics.

Radio Systems. Applied Electromagnetic Theory. High Frequency and Very High Frequency Research. Fre- quency Utilization. Modulation Research. Antenna Research. Radiodetermination.

Upper Atmosphere and Space Physics. Upper Atmosphere and Plasma Physics. High Latitude Ionosphere

Physics. Ionosphere and Exosphere Scatter. Airglow and Aurora. Ionospheric Radio Astronomy.

RADIO STANDARDS LABORATORY

Radio Standards Physics. Frequency and Time Disseminations. Radio and Microwave Materials. Atomic Fre- quency and Time-Interval Standards. Radio Plasma. Microwave Physics.

Radio Standards Engineering. High Frequency Electrical Standards. High Frequency Calibration Services. High

Frequency Impedance Standards. Microwave Calibration Services. Microwave Circuit Standards. Low Frequency

Calibration Services.

Joint Institute for Laboratory Astrophysics - NBS Group (Univ. of Colo.).