Air, Water and Soil Laboratories, Inc.

Virginia

Enthalpy Analytical, LLC

Delaware

Montrose Environmental Solutions, LLC

Delaware

ES Engineering Services, LLC

Delaware

FRS Environmental Remediation, Inc.

Florida

Montrose Air Quality Services, LLC

Delaware

Montrose Measurements and Analytics, LLC

Delaware

Montrose Services, LLC

Delaware

Nautilus Environmental, Inc.

California

Envirosystems, Incorporated

New Hampshire

Leymaster Environmental Consulting, LLC

California

PARS ENVIRONMENTAL, Inc.

New Jersey

Advanced GeoServices Corp.

Pennsylvania

Montrose Planning & Permitting, LLC

Delaware

Analytical Environmental Services

California

Environmental Planning Specialists, Inc.

Georgia

Montrose Waste-to-Resources, LLC

Delaware

Montrose Water and Sustainability Services, Inc.

Delaware

Target Emission Services USA, LLC

Texas

1203524 B.C. Ltd.

British Columbia

Target Emission Services Inc.

Alberta

LEHDER Environmental Services Limited

Ontario

Emerging Compounds Treatment Technologies, Inc.

Massachusetts

Montrose Foreign Holdings, Inc.

Delaware

The Center for Toxicology and Environmental Health, L.L.C.

Arkansas

CTEH Leasing, LLC

Arkansas

CTEH Properties, LLC

Arkansas

CTEH Government Services, LLC

Arkansas

CTEH IT Services, LLC

Arkansas