The M256 chemical agent detector (fig. 9-4) is a portable, expendable item that consists of a carrying case with straps, 12 sampler-detectors, one book of M-8 paper, and a set of operational instruction cards. You will use the samplerdetectors to test for chemical agents in the vapor form. The M-8 paper is used to check for chemical agents in the liquid form.
The 12 sampler-detectors are individually wrapped. Each sampler-detector consists of eight glass ampoules (each filled with chemical reagent), three test spots, a chemical heater, protective strips, and tabs. Each sampler-detector has instructions for its use printed on the outside of its protective bag. Formed channels in the plastic sheets direct the flow of the reagents from the finger-crushable ampoules to wet the test spots at the time of testing. SAFE/DANGER observations are printed on each sampler-detector. They show the approximate color that each spot develops if the agent is present and if it is absent.
To detect mustards (H and HD) and phosgene oxime (CX), the square test spot is used with the blister reagent ampoules and the chemical heater. To detect lewisite (L), the lewisite detecting tablet and the lewisite tablet rubbing tab are used. A pull tab covers the lewisite detecting tablet.
To detect hydrogen cyanide (AC) and cyanogen chloride (CK), the circular test spot is used with the blood reagent ampoules.
To detect nerve agents (V and G), the starshaped test spot is used with the nerve reagent ampoules.
The hinged protective strip, used in the closed position, protects the blood and nerve agent test spots. The colored beads in the ampoules have no operational function. They are installed during manufacture of the sampler-detector as an aid in identifying the sampler ampoules.
One book of M-8 chemical agent detector paper is also included in the M256 kit. Use the M-8 paper as discussed earlier in the chemical agent detection paper section of this chapter. One set of operational instruction cards is attached to the case by a lanyard. These cards contain instructions on the use of the M256 kit.
The M256 kit is a portable means for CBR monitoring teams to detect concentrations of nerve, blister, or blood agents; to differentiate between classes of agents; and to help determine when it is safe to remove CBR protective masks and clothing. The M256 kit has replaced the M15A2 chemical agent detector kit that was used just a few years ago.
When using the M256 kit to detect vapors in the air, you should use the following procedures:
1. Remove the three operational instruction cards from the kit. Read these instructions before proceeding.
2. Remove a sampler-detector from the kit. Check to ensure that it has not exceeded its discard expiration date. Do not use an outdated samplerdetector because it will not give you a reliable test indication.
3. Read the instructions on both sides of the protective bag before proceeding.
4. Open the sampler-detector bag by tearing
the bag along the tear line that is marked with arrows. Hold the sampler-detector on the windward side from you to keep from picking up vapors from your protective equipment. Do not allow excessive moisture, such as rain and dew, to come in contact with the sampler-detector.
5. Carefully remove the sampler-detector from its protective bag. Save the protective bag to refer to the instructions that are printed on it. Do not touch the sampler-detector agent test spots because incorrect test results may be produced.
6. Handle the sampler-detector carefully. Hold it by the hinged protective strip in the closed position. Keep the protective strip in the closed position to protect the test spots.
7. Swing the hinged heater assembly away from the test spot and discard the two loose protective strips under the hinged heater assembly.
Figure 9-4.-M256 chemical agent detector kit, front view. 9-17
Refer to figure 9-5 as we continue the discussion on the operating procedures for the M256 kit.
8. PuII off and discard the pull tab (marked 1) to expose the lewisite detecting tablet.
9. Rub the top half of the white paper side of the lewisite tablet rubbing tab (marked 2) on the lewisite detecting tablet. Repeat the rubbing until a mark is visible.
10. Hold the sampler-detector in the vertical position so that the ampoules are down.
11. Crush the four reagent ampoules in the three center pockets (marked 3) with your finger.
12. Rotate the sampler-detector until the test spots are in a down position. Force the liquid from the four ampoules through the formed channels to the test spots to ensure wetting.
13. Check to ensure that the hinged protective strip is over the test spots. Hold the
Figure 9-5.-Sampler-detector (protective bag removed).
sampler-detector horizontal with the left thumb over the center test spot.
14. Make sure that the hinged heater assembly is away from the test spot. The heater produces hot vapors and is hot to the touch. Keep the sampler-detector away from your face and bare skin once the ampoules have been broken.
15. Crush one of the two green ampoules (marked 4) with your finger. Immediately swing the hinged heater assembly over the test spot. Vent the vapor away from your body. Leave the hinged heater assembly in place for 2 minutes.
16. Swing the hinged heater assembly and the hinged protective strip away from the test spot after the 2 minutes have passed.
17. Hold the sampler-detector by the hinged protective strip.
18. Expose the test spots to the air for 10 minutes while shielding the sampler-detector from direct sunlight.
19. Crush the second green ampoule (marked
4) with your finger. Swing the hinged heater assembly over the test spot, and vent the vapor away from you. Leave the hinged heater assembly in place for 1 minute.
20. Swing the hinged heater assembly away from the test spot after 1 minute has passed.
21. Hold the sampler-detector vertically with the test spots down.
22. Crush the remaining ampoules (marked
5) with your finger. Force the liquid from the two ampoules through the formed channels to the test spots to ensure wetting.
23. Rerub the lewisite detecting tablet with the lewisite tablet rubbing tab. Make sure that the second rub mark is next to the first rub mark.
24. Immediately turn the sampler-detector over to determine whether safe or danger conditions exist. Observe the lewisite tablet rubbing tab for a difference in color between the two rub marks. Also, you can use the operational instruction cards to make a color comparison.
You can compare the blood agent and the lewisite tests immediately after the prescribed exposure time. The blister agents (H and CX) develop color immediately after all of the ampoules are broken. The nerve agent test requires a waiting period of 2 minutes. Disregard the small, blue areas under the plastic rim of the nerve agent spot. The blue coloring is caused by the humidity. The nerve spot may become difficult to wet with the solutions as the kit ages. You have to work the solutions to the spot carefully. At low concentrations, a change in the lewisite tablet rub
Figure 9-6.-M18A2 chemical agent detector kit.
mark may be very slight. Compare the first rub mark with the second rub mark before making a judgement. Yellow and orange colors sometimes occur on the blood test spot when no agent is present. A pink or blue color must be present for the test to be positive.
If the suspected surface contamination is in the form of a liquid, use the M-8 paper as discussed earlier. Keep the M256 kit stored in a cool, dry area when not in use. Be sure that the case is kept closed. Inspect the M256 kit completely before using to make sure you have all of the equipment needed. If any of the components are missing or the blood agent test spot is pinkish, do not use the sampler-detector.