<?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>0001205068</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>BULLS HERMAN E</nameOfPersonForWhoseAccountTheSecuritiesAreToBeSold>
      <relationshipsToIssuer>
        <relationshipToIssuer>Director</relationshipToIssuer>
      </relationshipsToIssuer>
    </issuerInfo>
    <securitiesInformation>
      <securitiesClassTitle>Common</securitiesClassTitle>
      <brokerOrMarketmakerDetails>
        <name>Charles Schwab Corp</name>
        <address>
          <com:street1>3000 Schwab Way</com:street1>
          <com:city>Westlake</com:city>
          <com:stateOrCountry>TX</com:stateOrCountry>
          <com:zipCode>76262</com:zipCode>
        </address>
      </brokerOrMarketmakerDetails>
      <noOfUnitsSold>2500</noOfUnitsSold>
      <aggregateMarketValue>1250000.00</aggregateMarketValue>
      <noOfUnitsOutstanding>35274843</noOfUnitsOutstanding>
      <approxSaleDate>06/09/2025</approxSaleDate>
      <securitiesExchangeName>NYSE</securitiesExchangeName>
    </securitiesInformation>
    <securitiesToBeSold>
      <securitiesClassTitle>Common</securitiesClassTitle>
      <acquiredDate>05/29/2021</acquiredDate>
      <natureOfAcquisitionTransaction>Grants for being a board member</natureOfAcquisitionTransaction>
      <nameOfPersonfromWhomAcquired>Issuer</nameOfPersonfromWhomAcquired>
      <isGiftTransaction>N</isGiftTransaction>
      <amountOfSecuritiesAcquired>2500</amountOfSecuritiesAcquired>
      <paymentDate>05/29/2021</paymentDate>
      <natureOfPayment>Equity Compensation</natureOfPayment>
    </securitiesToBeSold>
    <nothingToReportFlagOnSecuritiesSoldInPast3Months>Y</nothingToReportFlagOnSecuritiesSoldInPast3Months>
    <remarks>Client began selling on 6/9/25 so this filing is for 6/9/25. Account title: The Herman E. Bulls Revocable Trust U/A DTD 03/17/2016 - Herman E. Bulls as Trustee</remarks>
    <noticeSignature>
      <noticeDate>06/09/2025</noticeDate>
      <signature>Herman E. Bulls</signature>
    </noticeSignature>
  </formData>
</edgarSubmission>
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144
0001205068
XXXXXXXX
LIVE
0001035983
COMFORT SYSTEMS USA INC
001-13011
675 BERING DRIVE
SUITE 400
HOUSTON
TX
77057
7138309600
BULLS HERMAN E
Director
Common
Charles Schwab Corp
3000 Schwab Way
Westlake
TX
76262
2500
1250000.00
35274843
06/09/2025
NYSE
Common
05/29/2021
Grants for being a board member
Issuer
N
2500
05/29/2021
Equity Compensation
Y
Client began selling on 6/9/25 so this filing is for 6/9/25. Account title: The Herman E. Bulls Revocable Trust U/A DTD 03/17/2016 - Herman E. Bulls as Trustee
06/09/2025
Herman E. Bulls