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  <xsd:import namespace="http://www.xbrl.org/2009/role/negated" schemaLocation="http://www.xbrl.org/lrr/role/negated-2009-12-16.xsd" />
  <xsd:import namespace="http://fasb.org/us-roles/2022" schemaLocation="https://xbrl.fasb.org/us-gaap/2022/elts/us-roles-2022.xsd" />
  <xsd:import namespace="http://www.xbrl.org/2003/instance" schemaLocation="http://www.xbrl.org/2003/xbrl-instance-2003-12-31.xsd" />
  <xsd:import namespace="http://xbrl.org/2005/xbrldt" schemaLocation="http://www.xbrl.org/2005/xbrldt-2005.xsd" />
  <import namespace="http://fasb.org/us-gaap/2022" schemaLocation="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd" xmlns="http://www.w3.org/2001/XMLSchema" />
  <import namespace="http://fasb.org/srt/2022" schemaLocation="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd" xmlns="http://www.w3.org/2001/XMLSchema" />
  <xsd:element name="ContingentConsiderationObligationsMember" id="fix_ContingentConsiderationObligationsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" abstract="true" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="BusinessAcquisitionContingentConsiderationFairValueAtBalanceSheetDate" id="fix_BusinessAcquisitionContingentConsiderationFairValueAtBalanceSheetDate" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" abstract="false" nillable="true" xbrli:balance="credit" xbrli:periodType="instant" />
  <element id="fix_EffectOfUsingWeightedAverageCommonSharesOutstanding" name="EffectOfUsingWeightedAverageCommonSharesOutstanding" nillable="true" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="fix_ScheduleOfAdditionalMarginsTableTextBlock" name="ScheduleOfAdditionalMarginsTableTextBlock" nillable="true" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema" />
  <xsd:element name="DebtCovenantEffectiveDateAxis" id="fix_DebtCovenantEffectiveDateAxis" type="xbrli:stringItemType" substitutionGroup="xbrldt:dimensionItem" abstract="true" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="DebtCovenantEffectiveDateDomain" id="fix_DebtCovenantEffectiveDateDomain" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" abstract="true" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="DebtInstrumentVariableRateBaseRateMember" id="fix_DebtInstrumentVariableRateBaseRateMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" abstract="true" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="LetterOfCreditFeesPercentage" id="fix_LetterOfCreditFeesPercentage" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="PercentageOfBusinessWhichHasRequiredBonds" id="fix_PercentageOfBusinessWhichHasRequiredBonds" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="DebtCovenantRatioAxis" id="fix_DebtCovenantRatioAxis" type="xbrli:stringItemType" substitutionGroup="xbrldt:dimensionItem" abstract="true" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="DebtCovenantRatioDomain" id="fix_DebtCovenantRatioDomain" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" abstract="true" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="DebtCovenantRatioRangeOneMember" id="fix_DebtCovenantRatioRangeOneMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" abstract="true" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="DebtCovenantRatioRangeTwoMember" id="fix_DebtCovenantRatioRangeTwoMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" abstract="true" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="DebtCovenantRatioRangeThreeMember" id="fix_DebtCovenantRatioRangeThreeMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" abstract="true" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="DebtCovenantRatioRangeFourMember" id="fix_DebtCovenantRatioRangeFourMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" abstract="true" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="LossContingencySuretyAbstract" id="fix_LossContingencySuretyAbstract" type="xbrli:stringItemType" substitutionGroup="xbrli:item" abstract="true" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="LifeInsuranceContractsNumberOfEmployeesCovered" id="fix_LifeInsuranceContractsNumberOfEmployeesCovered" type="xbrli:integerItemType" substitutionGroup="xbrli:item" abstract="false" nillable="true" xbrli:periodType="instant" />
  <xsd:element name="LifeInsuranceContractsFaceAmount" id="fix_LifeInsuranceContractsFaceAmount" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" abstract="false" nillable="true" xbrli:balance="debit" xbrli:periodType="instant" />
  <element id="fix_StockIssuedDuringPeriodValueRestrictedAndPerformanceStockAwardGross" name="StockIssuedDuringPeriodValueRestrictedAndPerformanceStockAwardGross" nillable="true" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xbrli:balance="credit" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="fix_StockIssuedDuringPeriodSharesRestrictedAndPerformanceStockAwardGross" name="StockIssuedDuringPeriodSharesRestrictedAndPerformanceStockAwardGross" nillable="true" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="fix_LineOfCreditBorrowingCapacityAccordionOption" name="LineOfCreditBorrowingCapacityAccordionOption" nillable="true" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" xbrli:balance="credit" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="fix_DebtInstrumentVariableRateSecondaryClassificationAxis" name="DebtInstrumentVariableRateSecondaryClassificationAxis" nillable="true" type="xbrli:stringItemType" substitutionGroup="xbrldt:dimensionItem" abstract="true" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="fix_DebtInstrumentVariableRateSecondaryClassificationDomain" name="DebtInstrumentVariableRateSecondaryClassificationDomain" nillable="true" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" abstract="true" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="fix_DeferredAcquisitionPayments" name="DeferredAcquisitionPayments" nillable="true" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xbrli:balance="credit" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="fix_SubordinateDebtAndPromissoryNoteMember" name="SubordinateDebtAndPromissoryNoteMember" nillable="true" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" abstract="true" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="fix_StockRepurchaseProgram2007Member" name="StockRepurchaseProgram2007Member" nillable="true" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" abstract="true" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="fix_NewConstructionMember" name="NewConstructionMember" nillable="true" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" abstract="true" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="fix_ExistingBuildingConstructionMember" name="ExistingBuildingConstructionMember" nillable="true" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" abstract="true" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="fix_ServiceCallsMaintenanceAndMonitoringMember" name="ServiceCallsMaintenanceAndMonitoringMember" nillable="true" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" abstract="true" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="fix_EducationMember" name="EducationMember" nillable="true" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" abstract="true" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="fix_RetailRestaurantsAndEntertainmentMember" name="RetailRestaurantsAndEntertainmentMember" nillable="true" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" abstract="true" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="fix_MultiFamilyAndResidentialMember" name="MultiFamilyAndResidentialMember" nillable="true" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" abstract="true" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="fix_PercentageOfRevenueFromContractWithCustomer" name="PercentageOfRevenueFromContractWithCustomer" nillable="true" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="fix_RenewableServiceMaintenanceAgreementsTerm" name="RenewableServiceMaintenanceAgreementsTerm" nillable="true" type="xbrli:durationItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="fix_AmendedSeniorRevolvingCreditFacilityMember" name="AmendedSeniorRevolvingCreditFacilityMember" nillable="true" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" abstract="true" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="fix_ServiceProjectsMember" name="ServiceProjectsMember" nillable="true" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" abstract="true" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="fix_OfficeBuildingCustomerMember" name="OfficeBuildingCustomerMember" nillable="true" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" abstract="true" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="fix_HealthcareSectorCustomerMember" name="HealthcareSectorCustomerMember" nillable="true" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" abstract="true" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="fix_GovernmentCustomerMember" name="GovernmentCustomerMember" nillable="true" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" abstract="true" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="fix_NumberOfOptionsToRenew" name="NumberOfOptionsToRenew" nillable="true" type="xbrli:integerItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="fix_SupplementalInformationRelatedToLeasesAbstract" name="SupplementalInformationRelatedToLeasesAbstract" nillable="true" type="xbrli:stringItemType" substitutionGroup="xbrli:item" abstract="true" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="fix_ScheduleOfLeaseAssetsAndLiabilitiesTableTextBlock" name="ScheduleOfLeaseAssetsAndLiabilitiesTableTextBlock" nillable="true" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="fix_ScheduleOfSupplementalInformationRelatedToLeasesTableTextBlock" name="ScheduleOfSupplementalInformationRelatedToLeasesTableTextBlock" nillable="true" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="fix_VariableLeaseAndShortTermLeaseCost" name="VariableLeaseAndShortTermLeaseCost" nillable="true" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xbrli:balance="debit" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="fix_ElectricalServicesMember" name="ElectricalServicesMember" nillable="true" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" abstract="true" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="fix_MechanicalServicesIndustryMember" name="MechanicalServicesIndustryMember" nillable="true" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" abstract="true" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="fix_ElectricalServicesIndustryMember" name="ElectricalServicesIndustryMember" nillable="true" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" abstract="true" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="fix_ChangeInRightOfUseAssets" name="ChangeInRightOfUseAssets" nillable="true" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xbrli:balance="debit" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="fix_StockRepurchaseProgramAdditionalNumberOfSharesAuthorizedToBeRepurchased" name="StockRepurchaseProgramAdditionalNumberOfSharesAuthorizedToBeRepurchased" nillable="true" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="fix_MechanicalServicesMember" name="MechanicalServicesMember" nillable="true" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" abstract="true" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="fix_UnbilledAccountsReceivableAllowanceForCreditLoss" name="UnbilledAccountsReceivableAllowanceForCreditLoss" nillable="true" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" xbrli:balance="credit" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="fix_WeightedAverageCostOfCapital" name="WeightedAverageCostOfCapital" nillable="true" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="fix_LesseeOperatingLeaseLiabilityPaymentsDueAfterYearFour" name="LesseeOperatingLeaseLiabilityPaymentsDueAfterYearFour" nillable="true" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" xbrli:balance="credit" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="fix_FiniteLivedIntangibleAssetsAmortizationExpenseAfterYearFour" name="FiniteLivedIntangibleAssetsAmortizationExpenseAfterYearFour" nillable="true" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" xbrli:balance="debit" xmlns="http://www.w3.org/2001/XMLSchema" />
  <xsd:element name="DebtMaturityDateAxis" id="fix_DebtMaturityDateAxis" type="xbrli:stringItemType" substitutionGroup="xbrldt:dimensionItem" nillable="true" xbrli:periodType="duration" abstract="true" />
  <xsd:element name="DebtMaturityDateDomain" id="fix_DebtMaturityDateDomain" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="true" />
  <xsd:element name="MaturityYearOneMember" id="fix_MaturityYearOneMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="true" />
  <xsd:element name="MaturityYearTwoMember" id="fix_MaturityYearTwoMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="true" />
  <xsd:element name="MaturityYearThreeMember" id="fix_MaturityYearThreeMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="true" />
  <xsd:element name="MaturityYearFourMember" id="fix_MaturityYearFourMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="true" />
  <xsd:element name="AtlanticElectricLlcMember" id="fix_AtlanticElectricLlcMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="true" />
  <xsd:element name="IncomeTaxExaminationInterestIncomeExpenseNet" id="fix_IncomeTaxExaminationInterestIncomeExpenseNet" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="false" xbrli:balance="credit" />
  <xsd:element name="FederalIncomeTaxBenefitTaxCreditsResearch" id="fix_FederalIncomeTaxBenefitTaxCreditsResearch" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="false" xbrli:balance="credit" />
  <xsd:element name="TaxYears2019To2021Member" id="fix_TaxYears2019To2021Member" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="true" />
  <xsd:element name="RevenueRecognitionInitialApplicationPeriodCumulativeEffectTransitionAxis" id="fix_RevenueRecognitionInitialApplicationPeriodCumulativeEffectTransitionAxis" type="xbrli:stringItemType" substitutionGroup="xbrldt:dimensionItem" nillable="true" xbrli:periodType="duration" abstract="true" />
  <xsd:element name="RevenueRecognitionInitialApplicationPeriodCumulativeEffectTransitionDomain" id="fix_RevenueRecognitionInitialApplicationPeriodCumulativeEffectTransitionDomain" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="true" />
  <xsd:element name="OtherDebtLongTermAndShortTermCombinedAmount" id="fix_OtherDebtLongTermAndShortTermCombinedAmount" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="instant" abstract="false" xbrli:balance="credit" />
  <xsd:element name="DebtInstrumentVariableRateSecuredOvernightFinancingRateMember" id="fix_DebtInstrumentVariableRateSecuredOvernightFinancingRateMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="true" />
  <xsd:element name="DebtCovenantRatioRangeFiveMember" id="fix_DebtCovenantRatioRangeFiveMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="true" />
  <xsd:element name="CumulativeNumberOfCompaniesAcquiredOutstandingNotesToFormerOwners" id="fix_CumulativeNumberOfCompaniesAcquiredOutstandingNotesToFormerOwners" type="xbrli:integerItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="instant" abstract="false" />
  <xsd:element name="EldecoincMember" id="fix_EldecoincMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="true" />
  <xsd:element name="TechnologyMember" id="fix_TechnologyMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="true" />
  <xsd:element name="BusinessCombinationContingentConsiderationChangeInContingentConsiderationLiabilityMember" id="fix_BusinessCombinationContingentConsiderationChangeInContingentConsiderationLiabilityMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="true" />
  <xsd:element name="DisputeWithCustomerMember" id="fix_DisputeWithCustomerMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="true" />
  <xsd:element name="GrossProfitMember" id="fix_GrossProfitMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="true" />
  <xsd:element name="ManufacturingCustomerMember" id="fix_ManufacturingCustomerMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="true" />
</xsd:schema>
