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Proc-Type: 2001,MIC-CLEAR
Originator-Name: webmaster@www.sec.gov
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MIC-Info: RSA-MD5,RSA,
 DdkDlvAmSN7d+aHqGvJMthcD1gNtkgg+jsymQ/rmLCOsuWrCRr3IaCMi12U1Gcta
 099FcpcbvduGeadwZLm/XA==

<SEC-DOCUMENT>0001289895-10-000017.txt : 20100514
<SEC-HEADER>0001289895-10-000017.hdr.sgml : 20100514
<ACCEPTANCE-DATETIME>20100514165716
ACCESSION NUMBER:		0001289895-10-000017
CONFORMED SUBMISSION TYPE:	5
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20100331
FILED AS OF DATE:		20100514
DATE AS OF CHANGE:		20100514

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			SNEED PAULA A
		CENTRAL INDEX KEY:			0001193024

	FILING VALUES:
		FORM TYPE:		5
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-09344
		FILM NUMBER:		10834453

	MAIL ADDRESS:	
		STREET 1:		THREE LAKES DRIVE
		CITY:			NORTHFIELD
		STATE:			IL
		ZIP:			60093

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>5
<SEQUENCE>1
<FILENAME>edgar.xml
<DESCRIPTION>PRIMARY DOCUMENT
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0303</schemaVersion>

    <documentType>5</documentType>

    <periodOfReport>2010-03-31</periodOfReport>

    <form3HoldingsReported>0</form3HoldingsReported>

    <form4TransactionsReported>0</form4TransactionsReported>

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

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001193024</rptOwnerCik>
            <rptOwnerName>SNEED PAULA A</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O AIRGAS, INC.</rptOwnerStreet1>
            <rptOwnerStreet2>259 N. RADNOR-CHESTER ROAD, STE. 100</rptOwnerStreet2>
            <rptOwnerCity>RADNOR</rptOwnerCity>
            <rptOwnerState>PA</rptOwnerState>
            <rptOwnerZipCode>19087</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <derivativeTable>
        <derivativeTransaction>
            <securityTitle>
                <value>Phantom Stock</value>
                <footnoteId id="F1"/>
            </securityTitle>
            <conversionOrExercisePrice>
                <footnoteId id="F2"/>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2009-06-30</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>5</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>5.51</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>40.53</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <footnoteId id="F3"/>
            </exerciseDate>
            <expirationDate>
                <footnoteId id="F3"/>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>5.51</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>2333.2</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value></value>
                </natureOfOwnership>
            </ownershipNature>
        </derivativeTransaction>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">Acquired pursuant to Airgas, Inc.'s deferred compensation plan as a result of either (1) the deferral of director's compensation or (2) the reinvestment under the plan of dividends declared and paid with respect to shares of Airgas, Inc.'s common stock underlying the phantom stock.</footnote>
        <footnote id="F2">Each share of phantom stock represents the right to receive the cash value of one share of Airgas, Inc. common stock.</footnote>
        <footnote id="F3">Shares of phantom stock are payable in cash following the reporting person's termination of service as a director with Airgas, Inc.  The reporting person may transfer her phantom stock account into an alternative investment account under the plan at any time.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>Robert H. Young, Jr., Attorney-in-Fact for Paula A. Sneed</signatureName>
        <signatureDate>2010-05-14</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
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