Statement of Changes in Beneficial Ownership (Form 4)

FORM 4 Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b). Check this box to indicate that a transaction was made pursuant to a contract, instruction or written plan that is intended to satisfy the affirmative defense conditions of Rule 10b5-1(c). See Instruction 10.

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP OF SECURITIES Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934 or Section 30(h) of the Investment Company Act of 1940

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(Print or Type Responses)

1. Name and Address of Reporting Person * RICHEY VICTOR L JR 2. Issuer Name and Ticker or Trading Symbol CECO ENVIRONMENTAL CORP [CECO] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) __X__ Director _____ 10% Owner _____ Officer (give title below) _____ Other (specify below) (Last) (First) (Middle) 5080 SPECTRUM DRIVE, SUITE 800E 3. Date of Earliest Transaction (Month/Day/Year) 06/01/2026 (Street) ADDISON, TX 75001 4. If Amendment, Date Original Filed (Month/Day/Year) 6. Individual or Joint/Group Filing (Check Applicable Line) _X_ Form filed by One Reporting Person ___ Form filed by More than One Reporting Person (City) (State) (Zip) Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned

1.Title of Security (Instr. 3) 2. Transaction Date (Month/Day/Year) 2A. Deemed Execution Date, if any (Month/Day/Year) 3. Transaction Code (Instr. 8) 4. Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5) 5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4) 6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4) 7. Nature of Indirect Beneficial Ownership (Instr. 4) Code V Amount (A) or (D) Price Common Stock 06/01/2026 A 6,378 A (1)(2)(3) 6,378 D

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Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned
(e.g., puts, calls, warrants, options, convertible securities)

1. Title of Derivative Security (Instr. 3)

2. Conversion or Exercise Price of Derivative Security

3. Transaction Date (Month/Day/Year)

3A. Deemed Execution Date, if any (Month/Day/Year)

4. Transaction Code (Instr. 8)

5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4, and 5)

6. Date Exercisable and Expiration Date (Month/Day/Year)

7. Title and Amount of Underlying Securities (Instr. 3 and 4)

8. Price of Derivative Security (Instr. 5)

9. Number of Derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4)

10. Ownership Form of Derivative Security: Direct (D) or Indirect (I) (Instr. 4)

11. Nature of Indirect Beneficial Ownership (Instr. 4)

Code

V

(A)

(D)

Date Exercisable

Expiration Date

Title

Amount or Number of Shares

Restricted Stock Units

(4)

06/01/2026

A

2,215

(5)

(5)

Common Stock

2,215

$ 0

2,215

D

Reporting Owners

Reporting Owner Name / Address	Relationships
	Director	10% Owner	Officer	Other
RICHEY VICTOR L JR 5080 SPECTRUM DRIVE SUITE 800E ADDISON, TX 75001	X

Signatures

/s/ Kiril Kovachev as Attorney-in-Fact for Victor L. Richey Jr.		06/03/2026
**Signature of Reporting Person		Date

Explanation of Responses:

*	If the form is filed by more than one reporting person, see Instruction 4(b)(v).
**	Intentional misstatements or omissions of facts constitute Federal Criminal Violations. See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).
(1)	On June 1, 2026 (the "Closing Date"), pursuant to an Agreement and Plan of Merger, dated as of February 23, 2026 (the "Merger Agreement"), by and among CECO Environmental Corp. (the "Issuer"), Thermon Group Holdings, Inc. ("Thermon"), Longhorn Merger Sub, Inc. ("Merger Sub, Inc.") and Longhorn Merger Sub LLC ("Merger Sub LLC"), (i) Merger Sub, Inc. merged with and into Thermon, with Thermon continuing as a wholly-owned subsidiary of the Issuer and the surviving corporation of the merger (the "First Merger") and (ii) Thermon, as the surviving corporation of the First Merger, merged with and into Merger Sub LLC, with Merger Sub LLC being the surviving entity of the merger.
(2)	(Continued from Footnote 1) Pursuant to the Merger Agreement, at the effective time of the First Merger (the "Effective Time"), each share of Thermon's common stock issued and outstanding immediately prior to the Effective Time was converted into the right to receive, at the election of the holder and subject to the proration mechanisms set forth in the Merger Agreement, one of the following forms of merger consideration: (A) 0.6840 shares of the Issuer's common stock plus $10.00 in cash without interest (the "Mixed Election Consideration"), (B) $63.89 in cash, (C) 0.8110 shares of the Issuer's common stock (the "Stock Election Consideration"), or (D) for any shares of Thermon's common stock for which no election was made, the Mixed Election Consideration.
(3)	(Continued from Footnote 2) The Reporting Person elected to receive the Stock Election Consideration in exchange for his shares of Thermon common stock. As a result, the Reporting Person received 6,378 shares of the Issuer's common stock in exchange for shares of Thermon common stock held by the Reporting Person immediately prior to the Effective Time.
(4)	Represents restricted stock units granted under the CECO Environmental Corp. Deferred Compensation Plan for Non-Employee Directors. Each restricted stock unit represents a contingent right to receive one share of the Issuer's common stock and will vest on May 15, 2027.
(5)	Conversion of restricted stock units to the Issuer's common stock and distribution of such stock under the Deferred Compensation Plan is deferred until termination of service as a director.

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