-----BEGIN PRIVACY-ENHANCED MESSAGE-----
Proc-Type: 2001,MIC-CLEAR
Originator-Name: webmaster@www.sec.gov
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MIC-Info: RSA-MD5,RSA,
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 sjRCiFSEUu/vnIyt8j7n5g==

<SEC-DOCUMENT>0001323253-05-000015.txt : 20051114
<SEC-HEADER>0001323253-05-000015.hdr.sgml : 20051111
<ACCEPTANCE-DATETIME>20051114082953
ACCESSION NUMBER:		0001323253-05-000015
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20051110
FILED AS OF DATE:		20051114
DATE AS OF CHANGE:		20051114

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			CECO ENVIRONMENTAL CORP
		CENTRAL INDEX KEY:			0000003197
		STANDARD INDUSTRIAL CLASSIFICATION:	INDUSTRIAL & COMMERCIAL FANS & BLOWERS & AIR PURIFYING EQUIP [3564]
		IRS NUMBER:				132566064
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			1231

	BUSINESS ADDRESS:	
		STREET 1:		3120 FORRER STREET
		CITY:			CINCINNATI
		STATE:			OH
		ZIP:			45209
		BUSINESS PHONE:		4165936543

	MAIL ADDRESS:	
		STREET 1:		505 UNIVERSITY AVENUE
		STREET 2:		SUITE 1400
		CITY:			TORONTO
		STATE:			A6
		ZIP:			M5G 1X3

	FORMER COMPANY:	
		FORMER CONFORMED NAME:	API ENTERPRISES INC
		DATE OF NAME CHANGE:	19920703

	FORMER COMPANY:	
		FORMER CONFORMED NAME:	ALARM PRODUCTS INTERNATIONAL INC
		DATE OF NAME CHANGE:	19851210

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			Harvey Sandler Revocable Trust
		CENTRAL INDEX KEY:			0001323253
		STATE OF INCORPORATION:			FL
		FISCAL YEAR END:			1231

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	000-07099
		FILM NUMBER:		051196533

	BUSINESS ADDRESS:	
		STREET 1:		21170 N. E. 22ND COURT
		CITY:			NORTH MIAMI BEACH
		STATE:			FL
		ZIP:			33180
		BUSINESS PHONE:		954-389-7100

	MAIL ADDRESS:	
		STREET 1:		21170 N. E. 22ND COURT
		CITY:			NORTH MIAMI BEACH
		STATE:			FL
		ZIP:			33180
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>primary_doc.xml
<DESCRIPTION>PRIMARY DOCUMENT
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0202</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2005-11-10</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0000003197</issuerCik>
        <issuerName>CECO ENVIRONMENTAL CORP</issuerName>
        <issuerTradingSymbol>CECE</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001323253</rptOwnerCik>
            <rptOwnerName>Harvey Sandler Revocable Trust</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>21170 N. E. 22ND COURT</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>NORTH MIAMI BEACH</rptOwnerCity>
            <rptOwnerState>FL</rptOwnerState>
            <rptOwnerZipCode>33180</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>CECO ENVIRONMENTAL CORP</value>
            </securityTitle>
            <transactionDate>
                <value>2005-11-10</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>P</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>5500</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>4.256</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>1365243</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>CECO ENVIRONMENTAL CORP</value>
            </securityTitle>
            <transactionDate>
                <value>2005-11-11</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>P</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>6100</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>4.374</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>1371243</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <ownerSignature>
        <signatureName>Harvey Sandler, sole trustee of Harvey Sandler Revocable Trust</signatureName>
        <signatureDate>2005-11-14</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
-----END PRIVACY-ENHANCED MESSAGE-----