content: <?xml version="1.0" encoding="UTF-8"?><edgarSubmission xmlns="http://www.sec.gov/edgar/ownership" xmlns:com="http://www.sec.gov/edgar/common">
    <headerData>
      <submissionType>144</submissionType>
      <filerInfo>
        <filer>
          <filerCredentials>
            <cik>0001527678</cik>
            <ccc>XXXXXXXX</ccc>
          </filerCredentials>
        </filer>
        <liveTestFlag>LIVE</liveTestFlag>
  
  
  
      </filerInfo>
    </headerData>
    <formData>
      <issuerInfo>
        <issuerCik>0001035983</issuerCik>
        <issuerName>COMFORT SYSTEMS USA INC</issuerName>
        <secFileNumber>001-13011</secFileNumber>
        <issuerAddress>
          <com:street1>675 BERING DRIVE</com:street1>
          <com:street2>SUITE 400</com:street2>
          <com:city>HOUSTON</com:city>
          <com:stateOrCountry>MD</com:stateOrCountry>
          <com:zipCode>77057</com:zipCode>
        </issuerAddress>
        <issuerContactPhone>7138309600</issuerContactPhone>
        <nameOfPersonForWhoseAccountTheSecuritiesAreToBeSold>SANDBROOK WILLIAM J</nameOfPersonForWhoseAccountTheSecuritiesAreToBeSold>
        <relationshipsToIssuer>
          <relationshipToIssuer>Director</relationshipToIssuer>
        </relationshipsToIssuer>
      </issuerInfo>
      <securitiesInformation>
        <securitiesClassTitle>COMMON</securitiesClassTitle>
        <brokerOrMarketmakerDetails>
          <name>RBC WEALTH MANAGEMENT</name>
          <address>
            <com:street1>250 NICOLLET MALL, SUITE 1700</com:street1>
            <com:city>MINNEAPOLIS</com:city>
            <com:stateOrCountry>MN</com:stateOrCountry>
            <com:zipCode>55401</com:zipCode>
          </address>
        </brokerOrMarketmakerDetails>
        <noOfUnitsSold>7500</noOfUnitsSold>
        <aggregateMarketValue>1406250.00</aggregateMarketValue>
        <noOfUnitsOutstanding>35769739</noOfUnitsOutstanding>
        <approxSaleDate>09/12/2023</approxSaleDate>
        <securitiesExchangeName>NYSE</securitiesExchangeName>
      </securitiesInformation>
      <securitiesToBeSold>
        <securitiesClassTitle>COMMON</securitiesClassTitle>
        <acquiredDate>05/29/2018</acquiredDate>
        <natureOfAcquisitionTransaction>DIRECTORS COMPENSATION</natureOfAcquisitionTransaction>
        <nameOfPersonfromWhomAcquired>ISSUER</nameOfPersonfromWhomAcquired>
        <isGiftTransaction>N</isGiftTransaction>
        <amountOfSecuritiesAcquired>7500</amountOfSecuritiesAcquired>
        <paymentDate>05/29/2018</paymentDate>
        <natureOfPayment>N/A</natureOfPayment>
      </securitiesToBeSold>
      <nothingToReportFlagOnSecuritiesSoldInPast3Months>Y</nothingToReportFlagOnSecuritiesSoldInPast3Months>
      <noticeSignature>
        <noticeDate>09/12/2023</noticeDate>
        <signature>JEFFREY EISCHENS</signature>
      </noticeSignature>
    </formData>
  </edgarSubmission>
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text: 144
  0001527678
  XXXXXXXX
  LIVE
  0001035983
  COMFORT SYSTEMS USA INC
  001-13011
  675 BERING DRIVE
  SUITE 400
  HOUSTON
  MD
  77057
  7138309600
  SANDBROOK WILLIAM J
  Director
  COMMON
  RBC WEALTH MANAGEMENT
  250 NICOLLET MALL, SUITE 1700
  MINNEAPOLIS
  MN
  55401
  7500
  1406250.00
  35769739
  09/12/2023
  NYSE
  COMMON
  05/29/2018
  DIRECTORS COMPENSATION
  ISSUER
  N
  7500
  05/29/2018
  N/A
  Y
  09/12/2023
  JEFFREY EISCHENS