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Proc-Type: 2001,MIC-CLEAR
Originator-Name: webmaster@www.sec.gov
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MIC-Info: RSA-MD5,RSA,
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<SEC-DOCUMENT>0001289895-09-000078.txt : 20091112
<SEC-HEADER>0001289895-09-000078.hdr.sgml : 20091111
<ACCEPTANCE-DATETIME>20091112102205
ACCESSION NUMBER:		0001289895-09-000078
CONFORMED SUBMISSION TYPE:	4/A
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20091109
FILED AS OF DATE:		20091112
DATE AS OF CHANGE:		20091112

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			Hooper Max D
		CENTRAL INDEX KEY:			0001353625

	FILING VALUES:
		FORM TYPE:		4/A
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-09344
		FILM NUMBER:		091174922

	MAIL ADDRESS:	
		STREET 1:		259 N. RADNOR-CHESTER RD
		CITY:			RADNOR
		STATE:			PA
		ZIP:			19087

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			AIRGAS INC
		CENTRAL INDEX KEY:			0000804212
		STANDARD INDUSTRIAL CLASSIFICATION:	WHOLESALE-INDUSTRIAL MACHINERY & EQUIPMENT [5084]
		IRS NUMBER:				560732648
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			0331

	BUSINESS ADDRESS:	
		STREET 1:		259 N. RADNOR-CHESTER ROAD
		STREET 2:		SUITE 100
		CITY:			RADNOR
		STATE:			PA
		ZIP:			19087
		BUSINESS PHONE:		6106875253

	MAIL ADDRESS:	
		STREET 1:		259 N. RADNOR-CHESTER ROAD
		STREET 2:		SUITE 100
		CITY:			RADNOR
		STATE:			PA
		ZIP:			19087
</SEC-HEADER>
<DOCUMENT>
<TYPE>4/A
<SEQUENCE>1
<FILENAME>edgar.xml
<DESCRIPTION>PRIMARY DOCUMENT
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0303</schemaVersion>

    <documentType>4/A</documentType>

    <periodOfReport>2009-11-09</periodOfReport>

    <dateOfOriginalSubmission>2009-11-10</dateOfOriginalSubmission>

    <issuer>
        <issuerCik>0000804212</issuerCik>
        <issuerName>AIRGAS INC</issuerName>
        <issuerTradingSymbol>ARG</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001353625</rptOwnerCik>
            <rptOwnerName>Hooper Max D</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O AIRGAS, INC.</rptOwnerStreet1>
            <rptOwnerStreet2>259 N. RADNOR-CHESTER RD, STE. 100</rptOwnerStreet2>
            <rptOwnerCity>RADNOR</rptOwnerCity>
            <rptOwnerState>PA</rptOwnerState>
            <rptOwnerZipCode>19087</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>Division President-West</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2009-11-09</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>S</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>20800</value>
                    <footnoteId id="F1"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>47.86</value>
                    <footnoteId id="F2"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>15149</value>
                    <footnoteId id="F3"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value></value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">This Amendment to the Form 4 filed by the Reporting Person on November 10, 2009, is being filed to correct the Table 1-Item 4 disclosure reported therein to indicate that the Reporting Person disposed of (D) the shares in the reported transaction, rather than acquired (A) them.</footnote>
        <footnote id="F2">This price represents the average selling price (within a range of $47.82-$47.92) of the shares of common stock of Airgas, Inc. sold by the reporting person, as provided by the reporting person's broker.</footnote>
        <footnote id="F3">Includes 7,704 shares of Airgas, Inc. common stock acquired pursuant to Airgas, Inc.'s Employee Stock Purchase Plan (&quot;ESPP&quot;) as of 11/9/2009, the date of the latest available statement of the reporting person's ESPP holdings.  Since 3/31/2009, the date of the statement relied upon for the amount reported on the reporting person's 5/13/2009 Form 5, a total of 464 ESPP shares have been acquired in transactions exempt from Section 16(b).</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>Robert H. Young, Jr., Attorney-in-Fact for Max Hooper</signatureName>
        <signatureDate>2009-11-12</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
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