Name of the Subsidiary

State or Other Jurisdiction of Incorporation or Organization

Onterris Air Quality Services, LLC

Delaware

Onterris Australia Pty Ltd

Australia

Onterris Canada Inc.

Alberta

Onterris Foreign Holdings, Inc.

Delaware

Onterris Government Solutions, Inc.

Delaware

Onterris Laboratories, LLC

Delaware

Onterris Payroll, LLC

Delaware

Onterris Response & Recovery, LLC

Arkansas

Onterris Testing Canada Ltd.

British Columbia

Onterris Treatment Technologies, Inc.

Massachusetts

Onterris USA, Inc.

Delaware

Onterris Water and Sustainability Services, Inc.

Delaware

Environmental Intelligence, LLC

California

Environmental Standards, Inc.

Pennsylvania

FRS Environmental Remediation, Inc.

Florida

Montrose Environmental Group AB

Sweden

Montrose Environmental Group GmbH

Germany

Montrose Environmental Group BV

Belgium

MSE Group, LLC

Texas

PARS Environmental, Inc.

New Jersey

SensibleIOT, LLC

California

Spirit Environmental, LLC

Texas

Sustainable Treatment Solutions, Inc.

New York