Research Highlights

Technology Performance Summary: Smiths Detection APD
2000^® Handheld Detector for Chemical Warfare Agents

All Hazards Receipt Facilities (AHRFs) were developed to prescreen for chemical, radiochemical, and explosive hazards in samples collected during suspected terrorist attacks. The technologies used in AHRFs are intended to screen samples prior to a full analysis, helping protect responders, laboratory workers, and others from potential injury.

Evaluations of these technologies are summarized in the technology evaluation report, Testing of Screening Technologies for Detection of Chemical Warfare Agents in All Hazards Receipt Facilities. The chemical warfare agents (CWAs) included in the report were chosen because they might be used during, or develop as a by-product from, a terrorist attack.

The screening technologies are intended:

• To be rapid and qualitative
• To be simple to use and of relatively low cost
• To indicate if samples contain hazardous chemicals of concern.

Not all of the technologies evaluated were deemed suitable for the AHRF, although they might be useful for responders on the scene.

Technology Evaluated: Smiths Detection APD 2000®

Sample Types Evaluated for Indication of: Sarin and sulfur mustard in vapor

Conclusions:
The Smiths Detection APD 2000^®:

• Reliably detected sulfur mustard vapor; however, when the hydrocarbon mixture interferent was added to the sulfur mustard vapor, it gave no response. This testing resulted in an accuracy of 75% for sulfur mustard.
• When testing sulfur mustard at high temperature and relative humidity conditions (defined in Table 1, footnote b), test operators observed that, without intervention from them, the APD 2000^® switched into its auto calibration mode multiple times.
• Did not reliably respond to sarin in vapor.
• Typically responded within 30 seconds.
• Uses a relatively simple procedure.
  

Technology Description and Requirements: This instrument is a handheld detector for vapor phase CWAs based on the principle of ion mobility spectrometry (IMS). Molecules in the sampled air are ionized by a small radioactive source, and the ions are then separated by their drift in air at atmospheric pressure in an electrical field inside the instrument. The time/intensity pattern of the ion signal is used to identify the target chemicals. This instrument is battery powered and draws its sample air using an internal pump. Displays include a relative intensity indication, identification of the type of CWA detected, and visible and audible alarms. A confidence check sample, consisting of a source of simulant vapor, was supplied with the APD 2000^®. This source was used to confirm proper performance of the detector at the start of each day of testing, and this check was repeated as needed during performance of testing.

Testing Methodology and Results: Testing was conducted on one CWA at a time. To evaluate the technology (i.e., instrument), a flow of clean air passed through a clean air plenum, and an equal flow of air containing the tested gas passed through another plenum: the challenge plenum. The instrument was connected to a 4-way valve, through which clean air or the tested gas flowed before being vented into a chemical laboratory hood. The technology was first exposed to the clean air flow. After this, the 4-way valve was switched to the challenge plenum to deliver the CWA gas. The sequence of exposure to clean air followed by exposure to the CWA gas was carried out three successive times for the technology. This sequence was followed for each CWA and condition identified in Table 1. For this evaluation, a hydrocarbon mixture interferent was added to the blank or CWA gas at a ratio of 1:100 interferent mix to air flow.

Table 1: Summary of Smiths Detection APD 2000^® Test Results

^aA hydrocarbon mixture was used as the interferent.
^bTemperature and relative humidity conditions for vapor tests were: Base = 20 °C and 50% relative humidity, Low = 10 °C and 20% relative humidity, and High = 30 °C and 80% relative humidity.
^cAEGL = Acute Exposure Guide Level
^dOnly one positive response was observed and that occurred with clean air, the sample blank.

Contact: Eric Koglin

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