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 Autoclave Safety Guidelines


1.         Introduction

Autoclaves use pressurised steam to destroy micro-organisms, and, where appropriate, are the most dependable systems available for the decontamination of laboratory waste and the sterilisation of laboratory glassware, media, and reagents.

Note: Some materials are unsuitable for autoclaving and may explode or produce toxic or corrosive fumes. A COSHH assessment should be carried out regarding the suitability of materials for autoclaving.

To ensure the health and safety of staff, students and others who may be affected, Health and Safety regulations require the provision of safe systems of work, that operators, supervisors and maintenance staff are properly trained and that equipment such as autoclaves are properly inspected and maintained.

 2.        Scope

IMPORTANT: These are only general guidelines covering most of the relevant safety issues in use of autoclaves. They are not exhaustive and each autoclave and its particular use should be assessed to identify the individual hazards present.

3.         Hazards

The following are general hazards associated with the use of autoclaves:

  • Explosive displacement of the door - if the door is not properly secured while under internal pressure
  • Violent opening of the door if under residual pressure
  • Scalding from steam, vapour, hot liquid
  • Explosion of sealed containers
  • Cuts from broken glass
  • Burns
  • Fumes from toxic / corrosives materials eg formaldehyde
  • Infection from inadequately autoclaved materials

4.         Choice and performance

The relevant British Standard covering use of autoclaves in laboratories is BS 2646 Autoclaves for Sterilisation in Laboratories 1993 and BSEN 12347: 1998 Performance criteria for steam sterilisers and autoclaves. When Schools are purchasing autoclaves or arranging maintenance work they should always check that the autoclave and the associated installation and servicing comply with the British Standard specifications. The need for any additional controls such as HEPA filters on the exhaust for autoclaves in Containment Level 3 laboratories should be determined by risk assessment.

5.         Responsibility

Management Responsibility

Heads of School/Directors are responsible for ensuring that this guidance is implemented within the School/Centre.

Directors of Research and Principal Investigators are responsible for ensuring that researchers, technicians and other staff under their supervision or control adhere to the procedures outlined within this guidance.

Staff/Student Responsibility

Staff and students have the responsibility to carry out their research or other activities involving the use of autoclaves in accordance with the requirements of this policy.     

6.         General Precautions

All work involving the use of autoclaves must be the subject of a suitable and sufficient risk assessment and safe operating procedures developed.

The Safe Operating Procedures must be displayed beside each autoclave and adhered to at all times.

Before using an autoclave, authorised operators should have completed appropriate training provided by a person deemed competent by the Director of Centre / Head of School.

7.         Autoclave Bags

Autoclave (polypropylene) bags are tear resistant but can be punctured or burst in the autoclave and should be placed in a rigid container during autoclaving. Some are printed with an indicator that changes colour when processed. It is preferably to use plain printed bags without ‘biohazard’ printed on the outside. A ‘biohazard’ label should be placed on the bag holder and any containers used to transport or hold the material prior to sterilisation.

Polypropylene bags are impermeable to steam, and for this reason should not be twisted and taped shut, but gathered loosely at the top and secured with autoclave tape or stapled x3 along the top of the bag.  This will create an opening through which steam can pass.

Autoclave indicator tape should be applied to distinguish processed and unprocessed items, however a colour change in the tape is not a guarantee of sterility.

8.         Preparation of Materials

Fill liquid containers to a maximum of two thirds full.

Loosen caps or use vented closures

Autoclave bags should be filled to a maximum of two thirds full

Double bag if leakage is likely to occur

No more than 1kg of high insulating material per autoclave bag. Material with a high insulating capacity (animal bedding, high sided polypropylene containers) increases the time needed to reach sterilising temperatures.

9.         Time Selection

In determining the time, the size of articles to be autoclaved must be taken into consideration. A 2 litre flask containing 1 litre of liquid takes longer to sterilise than four 500ml flasks each containing 250ml.

Material with a high insulating capacity increases the time needed to to reach sterilising temperatures.

Autoclave bags containing biological waste should be autoclaved for a minimum of 30 minutes at 121 oC (or 20 minutes at 132 oC) to ensure sterilisation.

10.       General Safety Guidelines during Use

  • Review the operating manual/instructions prior to operation.
  • Wear appropriate personal protective equipment (lab coat safety glasses and heat resistance gloves. Suitable shoes must be worn (no open toed sandals or shoes).
  • Open the autoclave slowly and stand to the side or the back of the door in case of the release of hot steam from the previous cycle.
  • Place the autoclave bag containing the waste in a secondary containment vessel to retain any leakage (eg. Molten agar) that might occur.
  • Leave space between items/bags to allow the steam to circulate. Do not over load.
  • Select the appropriate cycle for the load, liquid/dry/waste.
  • To prevent scalding or boiling over, prior to removal allow liquids to cool down for 15-20 minutes after the cycle has completed.
  • When liquids are being sterilised, the autoclave should not be opened above 80oC, preferably lower.
  • No attempt should be made to override the autoclave’s built in safety control features.
  • Any malfunction or equipment faults should be reported immediately to the line manager / supervisor and remedial action taken.
  • Do not open the autoclave unless the cycle is complete, the pressure gauge indicates atmospheric pressure and the exhaust valve has been opened.

11.       Disposal

Consult the Waste Disposal Procedure for the correct waste stream for the disposal of waste.

Autoclaved liquid waste can normally be disposed of via the drain (public sewage system).

Autoclaved solid waste can normally be discarded via the general waste stream in black bags.

Attach a completed ‘Made Safe for Disposal’ label as set out in appendix 1 of the University’s Waste Disposal Procedure.

12.       Maintenance and Testing

Autoclaves should be cleaned and maintained in accordance with the manufacturer’s instructions eg. cleaning of the seals.

Where available, pressure / temperature graphs of the operating cycle of autoclaves should be kept and retained for 12 months. For autoclaves used to sterilise Group 2 pathogens and genetically modified organisms, spore vials should be used to test the efficacy of the autoclave every 2-3 months and records kept.

The performance of all autoclaves should be checked and validated by a qualified engineer every 6-12 months. A statutory insurance inspection must be carried out by an engineer appointed by the University’s insurers every 12-14 months. For this to occur, all autoclaves must be notified to the Estates’ Maintenance Services Manager for inclusion of the appropriate register.       

13.       Information, Instruction and Training

All staff and students who operate autoclaves must be provided with adequate information, instruction and training and be competent on their safe use and maintenance.

Large autoclave facilities used for the sterilisation of infected laboratory or other clinical waste materials, should be managed by a designated Laboratory Manager. To ensure continuity of use and that safety checks are carried out correctly, autoclaves should only be operated by trained and experienced University Staff. Large autoclave facilities should not be operated by postgraduate students or inexperienced research staff without appropriate oversight.

14.       Supervision

 Laboratory supervisors must ensure that where autoclaves are provided, that all procedures are followed by staff and students, particularly new or inexperienced users.

15.       Record Keeping

 All Schools must keep a register of autoclaves along with maintenance and test certificates. Copies of records should be available for audit.

16.       Monitoring/Audit

Schools/Directorates should monitor the compliance of this guidance particularly the testing and maintenance requirements. Records of maintenance events, instruction and training, etc. should be made available for audit by internal/ external auditors.

17.       Regulations & Guidance

Control of Substances Hazardous to Health Regulations (Northern Ireland) 2005 (SR 2003/34) as amended.

Pressure Systems Safety Regulations (Northern Ireland) 2004

Management of Health and Safety at Work Regulations (Northern Ireland) 2000

Provision and Use of Workplace Equipment Regulations (Northern Ireland) 1999