Practical Considerations for Optimal Collection of Trace Explosive Residue

Marcela Najarro, Jessica Staymates, Ed Sisco, Jeff Lawrence, Matthew Staymates, Jennifer Verkouteren, and Greg Gillen

Materials Measurement Science Division (MMSD)

National Institute of Standards and Technology, Gaithersburg, MD 20899 

Objectives

● To develop a training module that complements any existing ETD

training with sampling best practices supported by scientifically

validated data.

● Provide the end-user with “Why do you do things the way you do?”

● Factors considered: clear and concise training material, COTS

consumables, and interactive hands-on training.

● Complete prototype training module where the feasibility of

standardizing and/or optimizing sampling is quantitatively

demonstrated.

Introduction

● Sampling is the most critical step in the trace detection analysis chain.

● If sufficient explosive residue is not effectively transferred from a

surface to the collection media, ETD analysis will result in NO ALARM.

● The most impactful way to disseminate laboratory findings to the field

is education and training.

Smart Sampling: PAD 

● Pressure: Laboratory data suggests that a higher applied force

improves collection of the explosive residue

● Area of the wipe: Wipes have a “sweet spot” defined by the ETD

desorber size; Explosive particles collected outside of that target area

will not be analyzed.

● Area of the sample: Virtual threat collection simulations suggests that

the more area of the sample covered during swiping, the more

probable interaction with the threat becomes.

● Direction: One direction swiping pattern prevents the loss of collected

explosives particles.

Science Behind Pressure 

● Studies using RDX particles show that

the alarm rate of three different ETDs

significantly increased as a function

of pressure applied while swipe

sampling.

● Sample collection studies show that

collection efficiency improves as a

function of increasing pressure.

Sampling Pitfalls 

Conclusions

Angle of the wand 

Hands-On Training: PAD 

● Pilot study (131 participants) completed where

the feasibility of standardization and/or

optimization of sampling practices was

quantitatively demonstrated.

● Demonstrable increases in both applied pressure

and sampled area were noted after training.

● Plans to transition training module to institutional

training for end-users in a variety of environments.

• Every contact 

leaves a trace. 

• Explosives 

contamination 

is persistent. 

Science Behind Target Area 

● Deployed ETDs use a

thermal desorber to

heat a particular

area on the wipe.

● It is critical to know

the location of the

sweet spot for the

type of wipe and

detector used.

Training Validation ● Tekscan is a pressure

mapping system capable of

measuring applied pressure

and coverage area over a

test surface.

● Integrated software provides

real-time performance

feedback.

● Quantify effectiveness of training (benchmark vs. post training)

● Quantify end-user performance (recurrent training)

Potential Forensic Applications 

● Explosives Detection Field Kits

● Trace Evidence Field Collection

● Methamphetamine Remediation

● Nuclear Forensics

● National Institute of Occupational

Safety and Health – Anthrax

Commercialization 

of NIST R&D

Portions of this material are based upon work supported by the DHS Science and Technology Directorate,

Test and Evaluation and Standards Office, Acquisition Support & Operations, under Interagency Agreement

IAA HSHQPM – 14-X-0098 with the National Institute of Standards and Technology (NIST).