TWGFEX Laboratory Explosion Group 

Standards & Protocols Committee 

Recommended Guidelines for Forensic Identification of Post-Blast Explosive Residues 

1.1 Introduction: 

The purpose of this document is to set forth guidelines for the forensic identification of 

post-blast explosive residues. It is recognized that the correct characterization and/or 

identification of an explosive residue depends on the use of scientifically acceptable 

analytical methods and the expertise of the analyst. Unique requirements in different 

jurisdictions may dictate practices followed by a particular laboratory. This document 

does not discourage the use of any particular method within an analytical scheme and 

recommends the use of multiple techniques based on different principles and 

methodologies. Analytical chemistry is an advancing science and there are other 

analytical techniques which are not listed in the document but which may be employed 

in the identification of post-blast explosive residues. 

1.2 Categorizing Analytical Techniques: 

For purposes of this document, techniques for the analysis of post-blast explosive 

residues may be broken down into four categories: (1) those that provide significant 

structural and/or elemental information, (2) those that provide limited structural or 

elemental information, (3) those that provide a high degree of selectivity, and (4) those 

that are useful but do not fall in either of the other categories. Table 1 lists examples of 

such techniques based on the 1999 TWGFEX survey of explosion debris analysts in the 

United States. 

Table 1: Categories of Analytical Techniques 

Categories 1 and 2 Category 3 Category 4 

Infrared Spectroscopy (IR) Gas Chromatography (GC) Flame Test 

Gas Chromatography/Mass Spectrometry 

(GC/MS) 

Gas Chromatography Thermal Energy 

Analyzer (GC-TEA or EGIS) Spot Test 

Energy Dispersive X-Ray Analyzer (EDX) Liquid Chromatography (LC) Melting Point 

Raman Spectroscopy Liquid Chromatography Thermal Energy 

Analyzer (LC-TEA) 

X-Ray Diffraction (XRD) Ion Chromatography (IC) 

Liquid Chromatography/ Mass 

Spectrometry (LC/MS) Capillary Electrophoresis (CE) 

Thin Layer Chromatography (TLC) 

Ion Mobility Spectrometry (IMS) 

Polarizing Light Microscopy (PLM) 

Stereo Light Microscopy (SLM) 

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1.3 Recommended Practices: 

1.3.1 Good laboratory practices suggest that multiple techniques be employed in 

forensic post-blast explosive residue identification and that supporting analytical 

data be reviewable. Examples of such data include printed chromatograms, 

photographs/photocopies of results, or detailed descriptions of morphological 

characteristics. For any given component, the identification should be no less 

rigorous than the criteria found in The TWGFEX Guideline for the Forensic 

Identification of Intact Explosives (July 2004). 

1.3.2 If a method exists in the laboratory for the collection and analysis of volatile 

explosives and the exhibits have been properly packaged since collection at the 

scene (i.e. clean, properly sealed, airtight containers), conduct volatile sampling 

prior to opening the containers for other examinations. 

1.3.3 If applicable, conduct a macroscopical examination of the debris from the seat of 

the explosion and any visible residue in the vicinity. A microscopical examination 

of the area of interest is then conducted to determine if particulate matter is 

present which could be analyzed directly. The degree of usefulness of these 

initial observations assumes the examiner has experience in recognition of postblast explosive debris, residues and the associated physical damage. While the 

visual examination may be suggestive of the use of an explosive, it is necessary 

to use additional analytical techniques to identify the explosive compound itself, 

its key constituents or its residues. If particles of uninitiated explosive are found, 

follow the TWGFEX Guideline for the Forensic Identification of Intact Explosives 

(July 2004). If particulate matter if available, utilize suitable analytical methods to 

identify the components. An attempt should be made to identify the particulate 

matter prior to moving on to extractions. Suitable analytical techniques include 

FTIR, microcrystalline tests, PLM, IMS, EGIS, EDX, Raman, melting point and 

flame tests, although EDX and flame tests are not usually useful for 

characterizing organic materials. 

1.3.4 In the absence of particulate matter or if the analyses of the particulate matter did 

not identify the material, extractions of the debris should be made. Normally, 

aqueous extracts would be analyzed by IC, CE, LC, spot tests, microcrystalline 

tests and flame tests. Evaporated aqueous extracts are suitable for FTIR, XRD, 

EDX, Raman and PLM. Solvent extracts are normally analyzed by LC/MS, 

GC/MS, GC-TEA, EGIS, IMS, GC-ECD, FTIR and TLC. Suitable organic 

solvents in use are acetonitrile, acetone, ethanol, methanol, methylene chloride 

and ethyl acetate. 

1.3.5 For an analytical technique to be considered of value, the test must be 

considered ‘positive’. While ‘negative’ tests provide useful information for ruling 

out the presence of a particular family of explosives, negative results have limited 

value toward establishing the identification of an explosive substance. (i.e. a 

white crystal tested negative for nitrates with spot tests; this steered the 

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investigation toward improvised explosives even though it failed to identify the 

material) 

1.4 Interpretation of Results: 

1.4.1 Appendix A is a chart showing a list of explosives and their residues. It is 

possible to find uninitiated explosive as well as reaction products in a post-blast 

situation. (The chart is not necessarily all-inclusive but the species mentioned are 

known to have been identified in post-blast debris). 

1.4.2 Compiling a list of the materials identified is recommended, especially in the 

absence of unreacted materials. A review of the Appendix chart of explosives 

and their residues will help the analyst decide which explosives are possible 

sources. Since many post-blast materials are common to more than one 

explosive, it may be necessary to include more than a single source in the 

conclusion. 

1.5 Post-Blast Training Exercises: 

Forensic laboratories are encouraged to participate in controlled explosions of 

known explosives and the subsequent analysis of the post-blast debris to 

determine if their analytical methods are capable of detecting and identifying the 

explosives or their residues in post-blast situations. 

1.6 Safety: 

The laboratory is strongly encouraged to establish protocols for the safe 

execution of these procedures. 

1.6.1 Summary: 

It is understood that the forensic identification of post-blast explosive residues 

may be accomplished by a variety of analytical techniques. 

These guidelines were formulated with the express intent of application to postblast residues from both commercial and improvised explosives. 

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APPENDIX A 

Explosives and Their Post-Blast Residues 

EXPLOSIVE UNINITIATED OBSERVATION POSBlack Powder KNO3, C, S Sulfur smell, white smoke, 

visible grey residue 

SO 4 

SCN S2O

Pyrodex KNO3, C, S, DCDA, SB, 

KClO4 

Less sulfur smell and residue than black powder 

SO 4 

benzOCN 

Triple Seven KNO3, C, DCDA, SB, 

KClO4, 3-NBA 

No sulfur smell 

CO 3 

benzOCN 

Black Canyon/Clean Shot Pioneer/Golden Powder 

KNO3, C, S, ascorbic acid Sulfur smell, white smoke, 

visible grey residue 

SO4 SCN

Flash Powder Fuel [ Al, Mg, S ] and 

oxidizer 

Silvery residue ClO4 

oxid

Smokeless (single base) NC Unre

NC 

Smokeless (double base) NG, NC Unre

NC, 

Dynamite NG ester, AN/SN, other 

salts 

 Unre

NG, ions

PETN, RDX, HMX, EGDN, HMTD, Tetryl 

n/a Pare

foun

TNT TNT and often DNT’s TNT 

12 Feb 2007 Revision #6 
APPENDIX A 

Explosives and Their Post-Blast Residues 

EXPLOSIVE UNINITIATED OBSERVATION POSWater gels and Slurries Inorganic nitrate and 

sensitizer 

NO

3 

Emulsions Inorganic nitrates, waxes, 

sensitizers 

Al, smokeless powder particles & perchlorates, are sometimes present 

NO3 

ANFO AN and fuel oil NO3 

NO2 

Binaries AN, nitromethane Some have visible dyes NH 

4 

PBX Explosive, binder, 

plasticizer 

Black soot, some have dyes Unre

Primary explosives Metal + N3, (ONC)2 , 

C6H3O8N3 

Typically involve heavy metals such as lead, mercury, silver 

Unli(mayazid

Improvised Explosives/Incendiaries TATP C9H18O6 Peracetic acid, acetone, 

uninitiated material 

Peraacet

HMTD C6H12N2O6 Uninitiated material Hex

Dry ice + water in bottle CO2 delay - no smoke No c

charedge

Acetylene/natural gas/propane (often in a plastic bag) 

C2H2 lots of soot, lot of 

destruction, 

Confuse 

12 Feb 2007 Revision #6 
APPENDIX A 

Explosives and Their Post-Blast Residues 

EXPLOSIVE UNINITIATED OBSERVATION POSPool chlorine & an alcohol Ca(OCl)2, CaCl2, 

Ca(OH)2≅2H2O 

delay mechanism that can blow up if confined 

Cl2 o

Pool chlorine and brake fluid Ca(OCl)2, CaCl2, 

Ca(OH)2≅2H2O 

delay mechanism that can blow up if confined, white smoke, fireball 

Cl2 o

Pool chlorine and glycerin Ca(OCl)2, CaCl2, 

Ca(OH)2≅2H2O 

delay mechanism that can blow up if confined, fireball, white smoke 

Cl2 o

and 

Pool chlorine & milk products Ca(OCl)2, CaCl2, 

Ca(OH)2≅2H2O 

delay mechanism that can blow up if confined, white smoke, sour milk smell 

Cl2 o

Pool chlorine and oil (drying oils, 

vegetable oils, etc) 

Ca(OCl)2, CaCl2, 

Ca(OH)2≅2H2O 

delay mechanism that can blow up if confined 

Cl2 o

CaC

Ca(O

Ca(O

buty

Pool chlorine + antifreeze Ca(OCl)2, CaCl2, 

Ca(OH)2≅2H2O 

delay mechanism that can blow up if confined, fireball, white smoke 

Cl2 o

Pool chlorine (organic) and 

alcohol 

R-OH only works with organic pool product 

delay mechanism that can blow up if confined, grayish white smoke 

Cl2 o

ANTI (NI3) n/a Find 

stain 

unre

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APPENDIX A 

Explosives and Their Post-Blast Residues 

EXPLOSIVE UNINITIATED OBSERVATION POSChlorate & sugar n/a KCl 

suga

suga

Paper match heads (safety matches) 

KClO3, S, SiO2 sulphur smell KCl, 

fiber

mat

SO 4

Strike anywhere match heads P, S, KClO3, SiO2 sulphur smell Unre

head

- S2 , 

Red phosphorus and chlorate (Armstrong’s mixture) 

P, KClO3 

P, C

HCl and aluminum HCl, Al, H2O or Etchant 

(FeCl3 + H2O) and Al foil 

‘acid’ odor Al2C

uncoacid

HotPack or ActionPack Magnesium iron alloy, 

NaCl, silica and wetting agent 

steam Mag

Tannerite (see website for use) Al, finely divided AN Silvery residue Unre

NO2 

Mischmetal Ce, La, Nd, Fe sparks on impact Spa

mate

Urea nitrate n/a Unre

NO2 

12 Feb 2007 Revision #6 
APPENDIX A 

Explosives and Their Post-Blast Residues 

EXPLOSIVE UNINITIATED OBSERVATION POSAl and I2 n/a purple smoke, Unre

brow

50:50 Zn:S (both powders) Zn , S burns fast/explode in 

container, grey smoke 

Zn, 

CCl4 + Al powder (1:4) CCl4 , Al detonates Al Vaseline and KClO4 (1:2)(poor man’s C-4) 

KCLO4 , vaseline dark grey smoke 

needs detonator 

ClO4 mate

KMnO4 + glycerin KMnO4 , glycerin delay, deep purple smoke Unre

Drano + aluminum NaOH , Al delay, extra Al makes it work 

faster, generates H2 

Al, N

Al + lye/drano + water Al , KOH , NaOH , H2O generates H2 Al(O

Al + HCl Al , HCL generates H2 Al, A

12 Feb 2007 Revision #6 
APPENDIX A 

Explosives and Their Post-Blast Residues 

 Abbreviations Used : ECD 

 electron capture detector 

FID 

 flame ionization detector 

PDA 

 photo-diode array (detector) 

TEA 

 chemiluminescence detector 

EGIS 

 fast GC with chemiluminescence detector 

3-NBA 

3 nitro-benzoic acid 

SB 

 sodium benzoate 

DCDA 

dicyanodiamide 

PBX 

 plastic bonded explosives 

SN 

 sodium nitrate 

AN 

 ammonium nitrate 

MMA 

monomethylamine 

MMAN 

monomethylammonium nitrate 

EA 

ethanolamine 

EDDN 

 ethylenediamine dinitrate 

12 Feb 2007 Revision #6