White Paper

Combination Sterilisation Machines versus Central CSSD in Australian Healthcare

October 2026

Disclaimer

This content is provided for information only. The authors make no representation or warranty regarding the accuracy, completeness or currency of the content. No information in this whitepaper should be construed as medical advice. Readers should seek appropriate professional guidance before acting on any information contained in this document. The authors expressly disclaim all liability for any direct or indirect loss or damage arising from the use of or reliance on this information.

Introduction

This paper compares decentralised reprocessing, using washer-disinfectors and small steam sterilisers at the point of use, with centralised reprocessing in a central sterile services department (CSSD). It covers device classification, equipment selection, capacity, maintenance, failure risk, cost drivers, and water and energy use, and sets out selection criteria against AS 5369:2023. A cost model compares on-site reprocessing at a satellite unit with central reprocessing, with stated assumptions, a worked example and sensitivity analysis.

Device Classification

AS 5369:2023 classifies reusable devices by intended use. Critical devices are sterilised by moist heat, or by a low temperature process where they cannot withstand moist heat. Semi-critical devices are sterilised by moist heat, or receive thermal disinfection, high-level disinfection or low temperature sterilisation where they cannot withstand moist heat. Non-critical devices are cleaned and, where required, receive low or intermediate level disinfection.

AS 5369:2023 lists bedpans, urinals, sponge bowls and commodes as non-critical items that may require thermal disinfection in a washer-disinfector to ISO 15883-3 or ISO 15883-6. Do not clean bedpans manually. Most facilities therefore operate two systems: sterilisation of critical and semi-critical instruments, and point of use thermal disinfection of human waste containers.

Combination Machines

In this paper, combination machines are reprocessing machines installed outside the CSSD. The two common types are bedpan and utensil washer-disinfectors in dirty utility rooms, and small steam sterilisers in clinics, day procedure units and dental practices.

Bedpan and Utensil Washer-Disinfectors: These machines empty, flush, wash and thermally disinfect human waste containers and utensils in one chamber. Specify machines that conform to ISO 15883-1 and ISO 15883-3, and to ISO 15883-6 where other non-critical items such as wash bowls are processed. Confirm that type testing covers every item type and load configuration to be used. The thermal disinfection stage must deliver an A0 value of at least 60, equivalent to 80 deg C [176 deg F] for 1 min. Specify a selectable higher A0 value, e.g. A0 600, equivalent to 90 deg C [194 deg F] for 1 min, for use where the infection prevention risk assessment requires it. Specify hands-free operation and a door interlock that prevents opening before the cycle is complete. Do not process instruments in a bedpan washer-disinfector unless the machine is validated for that load.

Small Steam Sterilisers: Specify small sterilisers to EN 13060 and ISO/TS 22421. EN 13060 defines three cycle types. Type B cycles sterilise wrapped and unwrapped solid, porous and hollow loads. Type N cycles sterilise unwrapped solid items only. Type S cycles sterilise only the load types specified by the manufacturer. Do not sterilise packaged items in a cycle without a drying phase. A small steriliser outside the CSSD is subject to the same IQ, OQ, PQ, requalification, routine monitoring and traceability requirements as a CSSD steriliser.

Use Cases

• Hospital Wards: Install a bedpan washer-disinfector in each ward dirty utility room, located away from patient rooms. Consider modular units in isolation room ensuites. Return instruments and other critical devices to the CSSD. Apply point of use pre-treatment and contain used instruments for transport to a documented procedure.

• Small Hospitals and Day Procedure Units: Where there is no CSSD, provide an instrument washer-disinfector and a type B small steriliser in a dedicated reprocessing room that meets AS 5369:2023. Alternatively, outsource instrument reprocessing to an accredited provider under a written contract.

• Aged Care Facilities: Install bedpan washer-disinfectors in dirty utility rooms to process bedpans and commode pans after each use. Where podiatry, wound care or other procedures use reusable critical instruments, either reprocess on site to AS 5369:2023 or send instruments to a hospital CSSD or commercial provider. Risk assess transport between sites.

Central Sterile Services Department

A CSSD cleans, disinfects, inspects, assembles, packs, sterilises and stores reusable devices for one or more facilities. Typical equipment includes instrument washer-disinfectors, ultrasonic cleaners, large steam sterilisers to EN 285, low temperature sterilisers, drying cabinets and controlled storage. AS 5369:2023 advises that, wherever practicable, reprocessing should be centralised in a dedicated reprocessing facility.

Design the CSSD to segregate dirty and clean activities by physical barrier or spatial separation, with unidirectional workflow from dirty to clean. Develop a process map that controls cross-contamination risks, including airflows. Include pass-through washer-disinfectors and sterilisers in new or refurbished facilities. Use flush, smooth, non-shedding and water-resistant finishes, coved wall to floor junctions, sealed non-slip floors and fixed windows. Provide dedicated dirty and clean sinks that allow full immersion of devices. Design new facilities to AS 5369:2023 and the Australasian Health Facility Guidelines.

Off-site and Networked Services: A single CSSD may serve several facilities. Define responsibilities and conformance to AS 5369:2023 in a written contract, and obtain evidence of the provider's accreditation and quality activities. Risk assess transport between sites and document the transport conditions that make a device nonconforming. Size instrument inventory for the full transport and processing turnaround time.

Advantages of Decentralised Combination Machines

• Turnaround: Items are reprocessed immediately after use, which reduces the inventory required. Bedpans are available for reuse after one cycle.

• Waste Containment: Processing human waste containers in the dirty utility room avoids transporting soiled containers through the facility.

• Local Capacity: Reprocessing is independent of the CSSD schedule, transport rounds and operating hours.

• Small and Remote Facilities: On-site reprocessing removes dependence on courier schedules. Compare the cost per item of on-site reprocessing, including validation, maintenance and staff time, with the cost of outsourcing.

• Reduced Single-use Consumption: Reusable bedpans processed in a washer-disinfector avoid the purchase and disposal of pulp products. Compare whole of life cost per use for washer-disinfectors and macerators, including water, energy, detergent, pulp products, effluent and maintenance.

Disadvantages of Decentralised Combination Machines

• Maintenance and Testing Load: Each machine requires IQ, OQ, PQ, annual requalification, calibration, routine tests, planned maintenance and records. The workload increases with the number of machines and locations. Assign one competent person to coordinate testing and maintenance for all machines.

• Operator Competency: Point of use machines are operated by clinical staff with other duties. Include every operator in the reprocessing training program and assess competency at defined intervals. Confirm that the process record is checked and the load released by a competent person at every machine.

• Utilisation: Capacity cannot be shared between locations. Lightly loaded cycles increase water, energy and consumables per item. Size each machine for its local peak demand and record utilisation.

• Infrastructure: Each point of use reprocessing area must meet the AS 5369:2023 environment requirements. Each installation requires an adequately rated electrical supply, water to the specified quality, drainage and ventilation. Small sterilisers require feedwater to EN 13060.

• Single Point of Failure: A location with one machine has no local backup. Document the contingency for each location, e.g. access to a machine in an adjacent area, a loan unit or single-use bedpans, and specify the maximum repair response time in the service contract.

• Records and Traceability: Each steriliser must provide traceability to the individual cycle for every critical device. Standalone printers increase the manual record workload. Connect point of use sterilisers to the facility tracking system where available.

Advantages of Centralised CSSD

• Process Control: Dedicated reprocessing staff, one quality management system, uniform routine monitoring, and centralised calibration and water testing.

• Load Efficiency: Consolidated demand allows heavier loads, which reduces energy and water per kilogram processed.

• Equipment Range: Volume justifies low temperature sterilisers, endoscope reprocessors, ultrasonic cleaners, trolley washers and automated tracking, which individual units cannot support.

• Redundancy: Multiple machines of each type maintain service during breakdown and planned maintenance. Size the department to meet peak demand with the largest machine of each type out of service.

• Traceability and Recall: An integrated tracking system links each set to its cycle, operator and release. A failed load is identified and recalled from one record system.

Disadvantages of Centralised CSSD

• Turnaround and Inventory: Collection, processing and delivery time requires additional instrument sets. Calculate inventory from demand and total turnaround time.

• Logistics: Collection and delivery rounds, closed transport containers, lifts and vehicles add handling steps. Define transport containers, routes and schedules, and record handover at each step.

• Concentrated Risk: Loss of water, steam, power or the department itself stops reprocessing for every user. AS 5369:2023 requires a business continuity plan with documented backup procedures, e.g. reciprocal agreements with other CSSDs, standby power and a reserve of sterile sets.

• Capital and Space: A CSSD requires segregated areas, specified finishes, ventilation, water treatment and steam generation.

• Fixed Operating Cost: Staffing and standby losses do not scale down with volume. At low volume, cost per item rises. Switch off idle sterilisers between sessions.

• Urgent Requests: AS 5369:2023 does not provide comprehensive requirements for immediate-use sterilisation. Where it is used, define and validate the process. Otherwise hold spare sets for urgent cases.

• Human Waste Containers: Bedpans and urinals require processing at the point of use. A CSSD does not remove the need for ward washer-disinfectors.

Water and Energy

Steam Sterilisers: A study of one hospital steam steriliser over 304 days, published in Australian Health Review in 2017, measured 1.9 kWh/kg [0.86 kWh/lb] of electricity and 58 L/kg [6.9 US gal/lb] of water per load mass sterilised. Standby accounted for 40 % of electricity and 21 % of water. Electricity per kilogram fell from about 3 kWh/kg [1.36 kWh/lb] for 5 kg [11 lb] loads to 0.5 kWh/kg [0.23 kWh/lb] for 40 kg [88 lb] loads. Water per kilogram fell from about 200 L/kg [24 US gal/lb] to 20 L/kg [2.4 US gal/lb] over the same range. 32 % of standard cycles carried less than 15 kg [33 lb]. Consolidate loads to maximise mass per cycle, schedule cycles to minimise standby time, and switch off idle sterilisers. Specify vacuum and drain cooling systems that use water only during the cycle, and compare water and energy per cycle at full load in tenders.

Washer-Disinfectors: Water and energy use is driven by the number of fill and drain stages, the heating method and the disinfection temperature. Require each tenderer to state water and energy consumption per cycle for each cycle type, with the load and test method, and compare offers on that basis. Heat recovery and water recirculation are more readily justified on high-throughput CSSD machines.

Bedpan Processing: Washer-disinfectors use water, energy and detergent per cycle. Macerators use water and energy per cycle and require single-use pulp products. Confirm that macerator discharge is permitted under the local trade waste agreement.

Consumables: Packaging, chemical indicators and detergent use scale with cycle count. Consolidated loads reduce consumables per item in either model.

Cost Model

Scope: The model compares two ways of reprocessing the critical and semi-critical instrument sets used at a satellite day procedure unit. The on-site option is a dedicated reprocessing room with an instrument washer-disinfector and type B small sterilisers. The central option is transport to an existing CSSD with spare capacity. Bedpan processing remains at the point of use in both options and is excluded. Each tray is one instrument set. Values are illustrative, in Australian dollars at 2026 prices, excluding GST. Replace them with quoted prices, local wage rates and measured consumption.

On-Site Cost: Sum the annualised cost of the room and machines, maintenance and validation, handling labour, fixed daily labour for start-up, daily tests, cleaning and shutdown, training and quality oversight, daily air removal tests, utilities, and packaging and indicators. Calculate the number of machines of each type as daily trays divided by trays per machine per day, rounded up.

Central Cost: Sum the CSSD handling labour, utilities, packaging and indicators, transport, and the annual cost of the additional instrument sets needed to cover the longer turnaround. Additional sets equal daily trays multiplied by the additional turnaround in days. Where the CSSD has no spare capacity, add the annualised cost of the capacity required.

Annualisation: Convert capital to equivalent annual cost at a real discount rate of 5 %, using an annuity factor of 7.722 for a 10-year life and 12.462 for a 20-year life. Divide total annual cost by annual trays to obtain cost per tray.

Assumptions: The model uses the following values.

Basis: The CSSD steriliser values are the consumption measured at 40 kg [88 lb] loads by McGain et al. (2017). Washer-disinfector energy is the heat to raise 20 L [5.3 US gal] of water from 15 deg C [59 deg F] to 55 deg C [131 deg F] for the wash and 20 L [5.3 US gal] from 15 deg C [59 deg F] to 90 deg C [194 deg F] for thermal disinfection, 2.7 kWh in total, plus 1.0 kWh for chamber heating and drying, over 4 water stages of 20 L [5.3 US gal]. The CSSD machine uses 4 stages of 30 L [7.9 US gal], 4.0 kWh for water heating and 2.0 kWh for chamber heating and drying. The vehicle rate is the Australian Taxation Office cents per kilometre rate for 2026 to 2027. All other values are illustrative.

Worked Example

A satellite day procedure unit uses 20 trays per day, or 5,000 trays per year. On site, this requires one washer-disinfector and two small sterilisers. The near site is served by existing delivery rounds. The remote site is 100 km [62 mi] from the CSSD. Values are annual cost in Australian dollars.

Near Site: Central reprocessing costs A$7.64 less per tray, or A$38,187 less per year. The difference comprises A$26,118 of fixed on-site cost in excess of transport and additional sets, and A$18,750 from the higher on-site labour rate, less A$6,681 of lower on-site utilities. The fixed on-site cost of A$55,478 per year covers the room, machines, maintenance and validation, fixed labour, training, oversight and daily tests.

Remote Site: On-site reprocessing costs A$10.33 less per tray, or A$51,674 less per year. Transport is 40 % of the central cost.

Cost Structure: Handling labour is the largest single element in every option, at 33 % to 56 % of cost. Utilities are 2 % of on-site cost and 7 % of near site central cost. The CSSD steriliser values are measured values for one large hospital steriliser, and the on-site values are estimates. Measure both before relying on the difference.

Outsourcing: An external provider using the same transport and turnaround is cheaper than on-site reprocessing where its price is less than the on-site cost per tray minus transport and additional sets per tray. At 20 trays per day, the maximum price is A$28.65 per tray for the near site and A$10.68 per tray for the remote site.

Sensitivity

Volume: The following table gives cost per tray in Australian dollars by daily volume, with all other assumptions unchanged. On site, 5 and 10 trays per day need one machine of each type, 20 trays need one washer-disinfector and two sterilisers, and 40 trays need two washer-disinfectors and three sterilisers.

On-site cost per tray halves from 5 to 40 trays per day as fixed costs are spread over more trays. Central reprocessing is cheaper at every volume for the near site, and on-site reprocessing is cheaper at every volume for the remote site.

Transport: The following table gives the transport cost per day at which central and on-site reprocessing cost the same, by daily volume and additional turnaround. Central reprocessing is cheaper where transport costs less than these values.

Each additional turnaround day lowers the break-even transport cost, because the additional instrument sets are a cost of centralisation. Across these cases, the break-even transport cost is A$152 to A$337 per day.

Inputs: The following table gives cost per tray in Australian dollars at 20 trays per day, varying one input at a time.

No single input reverses the result for either site. At the same labour rate in both options, central reprocessing remains A$3.29 per tray cheaper for the near site. Repeat the calculation with quoted prices, local wage rates, measured handling times and the actual transport arrangement.

AS 5369:2023 Requirements

Scope and Timeframe: AS 5369:2023 applies wherever reusable devices are reprocessed, including hospitals, office-based practices, dental and podiatry practices, and aesthetics and body modification practices. It sets no implementation timeframe. Australian Commission on Safety and Quality in Health Care Advisory AS24/01 requires hospitals and day procedure services to complete a gap analysis by 30 June 2025 and implement a compliance plan with timeframes.

Equipment and Validation: Washer-disinfectors must conform to the applicable parts of ISO 15883. Large steam sterilisers must conform to EN 285 and ISO/TS 22421, and small steam sterilisers to EN 13060 and ISO/TS 22421. Perform IQ and OQ on each machine and PQ for each process on each machine. Requalify at least annually and after any change or repair that could affect the process. These requirements apply equally to point of use and CSSD equipment.

Point of Use Environment: Where reprocessing occurs at the point of use, provide a dedicated area or room separate from the patient treatment area. The area must meet the same requirements for environmental control, segregation of clean and dirty activities, unidirectional workflow, fixtures and finishes as a central facility. Where patient care and reprocessing share a room, they should not occur simultaneously. If they do, a risk assessment must show this is safe.

Traceability and Records: Trace each critical device to the individual cycle and steriliser. AS 5369:2023 advises that facilities should be working towards electronic tracking and process record systems.

Training: Provide a formal orientation and training program for all staff who reprocess devices, with competency assessed at intervals defined by the facility. The standard's guidance recommends annual training in infection prevention and control and in managing occupational exposure.

Continuity and Contracts: Maintain a business continuity plan with documented backup procedures. Where reprocessing, maintenance or testing is outsourced, define each party's responsibilities in a written agreement.

Selection Criteria

Select the reprocessing model for each device group using the following criteria.

• Infection Risk: Process human waste containers at the point of use. Centralise sterilisation of critical and semi-critical devices wherever practicable.

• Volume: Calculate cost per tray for each option, including capital, validation, maintenance, staff time, consumables, utilities, transport and the additional instrument sets needed for the longer turnaround. On-site fixed costs are spread over fewer trays at low volume.

• Transport and Turnaround: Centralisation is generally cheaper where an existing CSSD with spare capacity is reached on existing delivery rounds. On-site reprocessing or outsourcing is generally cheaper where transport is dedicated and costs more than about A$150 to A$340 per day. Calculate the break-even transport cost for the actual volume and turnaround.

• Compliance Capability: Where a point of use area cannot meet the AS 5369:2023 requirements for environment, validation, traceability and staff competency, centralise or outsource that process.

• Capacity and Redundancy: Confirm that each model maintains service with one machine out of service, and document the contingency for each location.

• Utilities: Compare water and energy per kilogram processed at expected load mass, including standby consumption.

For most hospitals, the resulting configuration is a bedpan washer-disinfector in each ward dirty utility room and centralised sterilisation of critical and semi-critical devices. Small facilities without a CSSD require a compliant dedicated reprocessing room or an outsourcing contract.

Sources

1. Standards Australia. AS 5369:2023 Reprocessing of reusable medical devices and other devices in health and non-health related facilities.
2. Australian Commission on Safety and Quality in Health Care. Transitioning from AS/NZS 4187:2014 to AS 5369:2023, August 2024.
3. Australian Commission on Safety and Quality in Health Care. Advisory AS24/01 Requirements for reprocessing of reusable medical devices in health service organisations.
4. Lobè C. Comparative analysis of bedpan processing equipment. AETMIS, ETMIS 2009, 5(4).
5. McGain F, Moore G, Black J. Steam sterilisation's energy and water footprint. Australian Health Review 2017, 41(1), pages 26 to 32.
6. Australian Taxation Office. LI 2026/19 Cents per kilometre deduction rate for car expenses, 2026 to 2027 income year.