Tear Gas Cleanup

Phase 1: Preparation, Containment, and Air Control

Before personnel enter, the area must be isolated to prevent cross-contamination and control airborne particles.

1. Site Isolation and PPE

• Establish PPE: All personnel must wear full personal protective equipment, including sealed safety goggles or full-face respirators, chemically resistant gloves, and disposable coveralls with hoods and boot covers.

• Safety Briefing: Review the Safety Data Sheet (SDS) for the specific tear gas agent used (CS or CN) to understand the required decontaminants and proper disposal methods.

2. Containment and Negative Air

• Critical Barriers: Seal off the affected area from all adjacent clean areas using 6-mil polyethylene sheeting taped securely to walls and floors. Seal all internal doors, windows, and non-essential openings within the work zone.

• HVAC System Shutdown: The building's Heating, Ventilation, and Air Conditioning (HVAC) system must be shut down and sealed at all supply and return registers within the containment zone. The ductwork itself is a significant reservoir for residue and must be addressed later.

• Negative Air Pressure: Install Air Filtration Devices (AFDs)—specifically, Negative Air Machines (NAMs)—fitted with HEPA filters and, ideally, a secondary bank of activated carbon filters (to capture Volatile Organic Compounds (VOCs) and chemical vapors). The NAMs must create and maintain a verifiable negative pressure differential inside the work area.

Phase 2: Removal of Contaminated Materials

Tear gas agents penetrate and absorb into porous materials. Unlike hard surfaces, these materials cannot be effectively decontaminated and must be removed.

1. Stripping the Structure

• Porous and Semi-Porous Materials: Systematically remove all textiles, upholstery, curtains, carpets, padding, and any paper or cardboard items.

• Disposal Protocol: All removed materials must be double-bagged in 6-mil poly bags, sealed with a gooseneck seal, and labeled as Hazardous Waste. Disposal must comply with local and state regulations for chemical debris.

• Insulation and Drywall: Depending on the severity of the deployment, it may be necessary to remove sections of drywall, ceiling tiles, and exposed thermal insulation, as these materials are highly porous and act as chemical sponges.

Phase 3: Chemical Decontamination (Cleaning)

Cleaning is done in stages, moving from gross removal to chemical neutralization.

1. Initial HEPA Vacuuming

• Dry Removal: Before wet cleaning, use HEPA-filtered vacuums (certified with sealed systems) to thoroughly vacuum all surfaces (walls, floors, hard furniture) to remove bulk, settled particulate residue. Avoid standard vacuums, which will re-aerosolize the CS particles.

2. Specialized Chemical Washing

• Decontaminant Solution: Use a cleaning solution recommended by the tear gas manufacturer or an industrial-grade degreaser/surfactant specifically designed to break down the chemical bonds of the CS or CN compound. Ammonia-based solutions should generally be avoided as they can react negatively with certain tear gas components.

• Three-Step Washing:

  1. Wash: Apply the decontaminant solution liberally using rags or sponges, working in small sections.

  2. Dwell Time: Allow the solution adequate dwell time (per manufacturer instructions) to chemically neutralize or solubilize the residue.

  3. Rinse/Wipe: Rinse the surface immediately with clean water and wipe dry using a new, disposable cloth.

• Procedure: Clean systematically from top to bottom (ceilings, walls, fixtures, then floors). Dispose of all spent wash and rinse water according to hazardous waste liquid protocols.

3. HVAC System Decontamination

• The ductwork must be professionally cleaned and decontaminated, typically using specialized rotary brushes and high-powered HEPA-filtered vacuum trucks. All internal HVAC components (coils, blowers, filters) must be cleaned or replaced, as they are key contaminant reservoirs.

Phase 4: Clearance Testing and Demobilization

The building is not safe until the air and surfaces are proven to be clean.

1. Final Clearance Verification

• Post-Cleaning Air Exchange: The NAMs should be allowed to run for an extended period to achieve several complete air exchanges.

• Surface Wipe Sampling: An independent third-party industrial hygienist must be hired to conduct surface wipe samples (using a solvent like methanol or a specialized sampling kit) of key hard surfaces (floors, windows, metal).

• Lab Analysis: Samples are sent to an accredited laboratory for quantitative analysis of CS or CN residue levels.

• Acceptance Standard: The hygienist verifies that all surface concentrations are below established cleanup criteria (often determined by local health departments or based on detection limits).

2. Demobilization

• Once clearance is granted, all final cleaning materials, PPE, and containment poly sheeting are bagged as contaminated waste and disposed of. The NAMs can be removed, and the HVAC system can be returned to operation.