Ergonomically designed height–adjustable isolator
The problems
The design of isolators has improved with each generation but there always remained difficulties in their use. The main difficulties requiring attention were:
- Tall people need to crouch and short people need to stretch. All parts of isolators cannot always be reached due to restrictions imposed by small glove ports and sleeve length. All inside surfaces cannot be reached for cleaning.
- Operators are forced into a poor posture, making manual handling difficult and hazardous.
- Often, a glove may be used with both the left and right hand. The traditional left and right handed gloves hinder handling.
- Balances in which the display is part of the balance require the operator to change posture making them difficult to read.
- Isolators that have the floors of the airlock and working chamber at different heights require containers to be lifted up and down over a door rim making handling more difficult.
Door opening
- Opening and closing a door is not always easy. Doorknobs can be difficult to turn, particularly with restrictive gloves and glove ports. Often containers have to be lifted and moved out of the way before a door can be opened and then lifted back into place once the door is shut.
Control issues
- Doors are not always interlocked. The outer door can be opened at the same time as the inner door leading to exposure.
- Some isolators have internal surfaces which cannot be reached through its gloves. This means that the front has to be raised so that it can be cleaned thoroughly. This leads to a risk of further exposure.
- Lighting maintained from inside the isolator can lead to a source of exposure when the tube is changed.
- Safe-change HEPA filters and pre-filters are required to avoid exposure when changing filters. Test ports are required for HEPA filter testing.
- Gloves can be difficult to fit with a “safe-change” technique.
Lighting and visibility
- Reflections from lighting lead to difficulties in reading the balance display.
- There is often restricted visibility due to opaque sleeves.
- Photographs illustrating these points are shown in the appendix.
The solutions
Following trials of alternative design isolator mock ups; an isolator was produced with the following features:
Manual handling
- Two electrically driven legs allow vertical movement between 1770mm and 2270mm. Movement is controlled by push buttons located at easy reach within the cabinet.
There are no changes of level within the isolator or airlocks. Therefore no lifting is required.
- A recess in the base of the isolator is designed to allow the balance to be located centrally and the balance scale is at the same height as the base of the isolator. Containers can therefore be moved onto the balance without lifting.
- The waste port is flush with the base of the isolator so that there is no requirement for containers to be lifted over the lid.
Glove design
- The glove ports have large diameters and do not restrict upper arm movements. Arms and shoulders are not forced into awkward postures and can move comfortably.
- The sleeves have been especially made to fit the large glove ports and are long enough to provide easy access to all parts of the isolator. They are made from transparent plastic to ensure the operator has better visibility.
- Ambidextrous gloves are fitted to the sleeve cuff so that they can be used easily with either hand.
Door opening
- All doors are electrically operated by flush mounted push buttons. They are interlocked to prevent the outer airlock doors being opened at the same time as the inner doors.
- Push button operation also ensures that the doors can be opened easily and comfortably without having to go through a series of manoeuvres.
Cleanability
- All surfaces are smooth and curved so that they are easy to clean. All inner surfaces are within easy reach. A sloped top is also easy to reach and clean on the inside.
- The front panel no longer needs to be lifted for cleaning although it still has this facility for use in exceptional circumstances.
Control of hazardous substances
- “Safe-change” gloves are fitted to the isolator so that they can be changed without breaking containment. A loop is fitted to assist removal and fitting. A double bag waste-disposal unit is contained in a dedicated air-lock.
- All doors, including the waste lid, are fitted with inflatable pneumatic seals (1.5bar), to give a secure all round seal.
- Internal lighting can be accessed externally without breaking containment.
- The isolator is under negative pressure to ensure containment.
- Double safe- change HEPA filters are fitted to exhaust. These are designed for easy removal. Again, design ensures containment during maintenance. A port fitted to give access for HEPA filter integrity testing.
- Visual and audible alarms will indicate loss of pressure and loss of air and operate simultaneously.
- Minihelic gauges show the pressure differential across the filters and the isolator.
Lighting
- Internal lighting is angled to reduce reflection. The balance display is flush mounted at eye level to make it easier to read.
The benefits
- Total cost of the isolator was £30,000. This is approximately £9,000 more than the cost of a conventional isolator but the benefits of the new design outweigh the additional costs.
- Has significantly reduced the operator exposure to the product.
- The height adjustable feature and larger arm holes has eliminated awkward ergonomic postures and poor manual handling techniques. This in turn, will reduce the prevalence of upper limb disorders and back complaints.
- Total containment reduces the risk of cross-contamination, which is vital to comply with current quality assurance pressures from Enforcing Authorities.
- The contribution of operators to the design process was a key factor in the acceptance of the new design.
- The isolator, unlike other control systems such as local exhaust ventilation has the flexibility to be moved to another area if required.
