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>0001479275</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>TX</com:stateOrCountry>
          <com:zipCode>77057</com:zipCode>
        </issuerAddress>
        <issuerContactPhone>7138309600</issuerContactPhone>
        <nameOfPersonForWhoseAccountTheSecuritiesAreToBeSold>Tang Vance W</nameOfPersonForWhoseAccountTheSecuritiesAreToBeSold>
        <relationshipsToIssuer>
          <relationshipToIssuer>Director</relationshipToIssuer>
        </relationshipsToIssuer>
      </issuerInfo>
      <securitiesInformation>
        <securitiesClassTitle>Common</securitiesClassTitle>
        <brokerOrMarketmakerDetails>
          <name>Fidelity Brokerage Services LLC</name>
          <address>
            <com:street1>245 Summer Street</com:street1>
            <com:city>Boston</com:city>
            <com:stateOrCountry>MA</com:stateOrCountry>
            <com:zipCode>02110</com:zipCode>
          </address>
        </brokerOrMarketmakerDetails>
        <noOfUnitsSold>4461</noOfUnitsSold>
        <aggregateMarketValue>1472130.00</aggregateMarketValue>
        <noOfUnitsOutstanding>35721909</noOfUnitsOutstanding>
        <approxSaleDate>05/15/2024</approxSaleDate>
        <securitiesExchangeName>NYSE</securitiesExchangeName>
      </securitiesInformation>
      <securitiesToBeSold>
        <securitiesClassTitle>Common</securitiesClassTitle>
        <acquiredDate>05/16/2023</acquiredDate>
        <natureOfAcquisitionTransaction>Stock Award</natureOfAcquisitionTransaction>
        <nameOfPersonfromWhomAcquired>Issuer</nameOfPersonfromWhomAcquired>
        <isGiftTransaction>N</isGiftTransaction>
        <amountOfSecuritiesAcquired>1065</amountOfSecuritiesAcquired>
        <paymentDate>05/16/2023</paymentDate>
        <natureOfPayment>Compensation</natureOfPayment>
      </securitiesToBeSold>
      <securitiesToBeSold>
        <securitiesClassTitle>Common</securitiesClassTitle>
        <acquiredDate>05/19/2016</acquiredDate>
        <natureOfAcquisitionTransaction>Stock Award</natureOfAcquisitionTransaction>
        <nameOfPersonfromWhomAcquired>Issuer</nameOfPersonfromWhomAcquired>
        <isGiftTransaction>N</isGiftTransaction>
        <amountOfSecuritiesAcquired>3396</amountOfSecuritiesAcquired>
        <paymentDate>05/19/2016</paymentDate>
        <natureOfPayment>Compensation</natureOfPayment>
      </securitiesToBeSold>
      <nothingToReportFlagOnSecuritiesSoldInPast3Months>N</nothingToReportFlagOnSecuritiesSoldInPast3Months>
      <securitiesSoldInPast3Months>
        <sellerDetails>
          <name>Tang Living Trust</name>
          <address>
            <com:street1>675 BERING DRIVE</com:street1>
            <com:city>Houston</com:city>
            <com:stateOrCountry>TX</com:stateOrCountry>
            <com:zipCode>77057</com:zipCode>
          </address>
        </sellerDetails>
        <securitiesClassTitle>COMFORT SYSTEMS USA INC</securitiesClassTitle>
        <saleDate>02/26/2024</saleDate>
        <amountOfSecuritiesSold>10000</amountOfSecuritiesSold>
        <grossProceeds>2830015.00</grossProceeds>
      </securitiesSoldInPast3Months>
      <remarks>Selling from Tang Living Trust</remarks>
      <noticeSignature>
        <noticeDate>05/15/2024</noticeDate>
        <signature>/s/ Cristina Garcia, as a duly authorized representative of Fidelity Brokerage Services LLC, as attorney-in-fact for Tang Vance W</signature>
      </noticeSignature>
    </formData>
  </edgarSubmission>
metadata_documents: [{"type": "144", "sequence": "1", "filename": "primary_doc.xml", "secsgml_size_bytes": 4036}]
text: 144
  0001479275
  XXXXXXXX
  LIVE
  0001035983
  COMFORT SYSTEMS USA INC
  001-13011
  675 BERING DRIVE
  SUITE 400
  HOUSTON
  TX
  77057
  7138309600
  Tang Vance W
  Director
  Common
  Fidelity Brokerage Services LLC
  245 Summer Street
  Boston
  MA
  02110
  4461
  1472130.00
  35721909
  05/15/2024
  NYSE
  Common
  05/16/2023
  Stock Award
  Issuer
  N
  1065
  05/16/2023
  Compensation
  Common
  05/19/2016
  Stock Award
  Issuer
  N
  3396
  05/19/2016
  Compensation
  N
  Tang Living Trust
  675 BERING DRIVE
  Houston
  TX
  77057
  COMFORT SYSTEMS USA INC
  02/26/2024
  10000
  2830015.00
  Selling from Tang Living Trust
  05/15/2024
  /s/ Cristina Garcia, as a duly authorized representative of Fidelity Brokerage Services LLC, as attorney-in-fact for Tang Vance W