12 Jul Clear & present dangers
The clean rooms that I am used to dealing with are in an industrial environment and staffed by the white-clad, respirator wearing professionals that are synonymous with this area write FME’s very own international Health & Safety expert Toby Hayward. However, when researching this feature, the prevalence of these facilities in a learning environment was new to me.
Clean rooms in universities and commercial research establishments fulfill a key role, as research work in many widely diverse fields would be virtually impossible without them. However, clean rooms are high risk areas, which is mainly due to the high cost of replacing any loss due to fire damage and
the consequential loss of revenue during the following reconstruction period.
Like all working environments providing adequate fire protection is essential, as a fire in a clean room could have devastating financial consequences, on top of the obvious danger to life and health.
Should a fire occur, the highest priority is the prompt activation of the predefined countermeasures. A fire protection system is therefore required that ensures a fast and reliable response. In addition to the warning and evacuation of all persons in the danger area, smoke and particulate must be prevented from spreading to any neighbouring clean rooms. In cases where a fire occurs outside the clean rooms, smoke and particulate must be prevented from entering and obviously the fire must be extinguished as soon as possible.
So, what is a clean room?
Clean rooms are enclosed areas where dust or smoke particles, airborne microbes, aerosol particles and chemical vapours (that are normally present in the environment) cannot be allowed, as they may cause unwanted contamination. A clean room separates the research processes from the “contaminated” environment, enabling the procedures to be carried out under carefully controlled environmental conditions.
Therefore, the main objectives of a clean room are: –
- To protect processes and products from contamination
- To protect persons from health – threatening substances and organisms (e.g. micro-organisms)
- To protect the environment from dangerous and unwanted emissions
Clean rooms are designed in such a way that:
The specified air quality level can be guaranteed
The climatic conditions remain within specified tolerance limits
Only authorised persons are permitted access; to prevent any adverse effects on the environmental conditions that might be caused by untrained persons
Each clean room is a separate fire compartment and is therefore in no immediate danger from a fire in a neighbouring fire compartment
A fire can be detected and dealt with at the earliest possible stage, thus preventing any impact on a neighbouring clean room
Fire protection objectives
1 Recognition of abnormal fire-related aerosol concentrations and transmission of this information to a technician. The situation can then be quickly evaluated and appropriate countermeasures taken (e.g. removing power from the relevant equipment).
2 Minimising damage by suppressing an incipient fire at the earliest possible stage using reliable residue free extinguishing system
3 Prevent smoke and fire spreading to other areas
4 Timely alerting and safe evacuation of all endangered persons.typical fire hazards
- Overload or short circuit of electrical or electronic equipment and installations
- Careless handling of heat sources such as hot air guns or Bunsen burners
- Leakages of highly inflammable or pyrophoric liquids (i.e. those liquids that can ignite spontaneously on contact with air or moisture)
- Explosive concentrations of gases or solvent vapours typical development of a fire
In a clean room we cannot talk about typical fire development.
To a great extent, this will depend on the infrastructure, materials and substances inside the clean room, together with the procedures being carried out.
- When electrical or electronic components overheat they generate increasing quantities of visible aerosols. If appropriate countermeasures are not taken at this stage, such as removing power from the devices concerned, then the smouldering fire can develop into an open fire. This can cause immense damage and create a significant threat to any persons in the area
- Careless handling of heat sources, spontaneous ignition of dust deposits in the ventilation ducts, or self-igniting liquids can lead directly to an open fire, which (depending on the fire load) may spread very rapidly
- An explosion (a rapid increase in volume and uncontrolled release of energy) can occur, if an explosive concentration of gases if allowed to build up critical points
- Even the smallest of fires can cause enormous damage
- High air circulation rates dilute the aerosol concentration, making it more difficult to detect incipient fires at an early stage
- Very little heat will be created by a smouldering fire and consequently the fire aerosols generated will not spread throughout the entire room
- To minimise fire damage, the consequences of a fire must be restricted to the clean room itself
- Fire aerosols from a neighbouring room must be prevented from entering
- An explosive mixture of gases must not be allowed to develop
- The extinguishing process itself must not cause any additional damage (e.g. the ruining of electronic equipment, water damage or other types of residue) solution
Depending on the area of application, clean room requirements can differ significantly. In the pharmaceutical industry topics such as particle emission, chemical stability or clean-ability play an important role.
Such topics, however, would not have the same importance in, for example, the photo-voltaic sector. Demands on the air purity can also vary considerably as they can be influenced by the outside air, contamination caused by personnel, process-dependent contamination and inappropriate production facilities.
Although clean room requirements may vary considerably, this has only a limited influence on the design of a suitable fire protection system. What is important, however, is that the ventilation conditions in the room are taken into consideration when selecting and positioning the appropriate detectors.
During an extinguishing incident the agent itself should not cause any additional damage. Consequently, the type of equipment and materials used in the room will largely determine the most appropriate extinguishing agents to be used.
Clean rooms are at the core of many diverse research projects and any contamination caused by dust, microorganisms or smoke particles can severely disrupt the research work. On the other hand, health and safety considerations also present their own particular challenges. Active substances (in pharmaceutical research projects), dangerous pathogenic bacteria (in a high security laboratory), flammable cleaning solvents and toxic chemicals all pose significant health risks for research personnel and for the environment.
On the organisational side the two most important factors are access control and training. It is important to ensure that only authorised persons who have received the necessary training are able to enter the clean room. In the case of universities it is essential that they receive adequate training, where the importance of the appropriate behaviour is impressed upon them.
In addition to training regarding the correct use of the equipment, topics such as technical cleanliness, the correct handling and safe disposal of the various materials (solids, liquids and gases) must also be dealt with. In this context special attention should be paid to the prevention of fire. It is also important, however, to be fully acquainted with the automated extinguishing system and how (and when) fire extinguishers should be used to deal with minor incidents.
Both clean room specific and fire protection aspects must be taken into consideration when designing and implementing the appropriate structural measures. As over pressure in a clean room can prevent pollutants from entering the room through the air, the room-in-room construction is often the predefined design concept. For this reason the experts responsible for the clean room system design must be consulted to help provide a suitable smoke extraction solution.
Fire protection incorporates a wide range of technical disciplines and dedicated systems including access control, gas warning, fire detection and extinguishing. The access control system should ensure that only authorised persons (who have received the appropriate training) are permitted entry into the clean room. The gas warning system must be able to prevent the development of any dangerous gas mixtures by controlling the ventilation in the individual areas. In case of a dangerous situation arising (e.g. due to the malfunction of the ventilation system) it must also generate a warning signal, and an alarm if the danger becomes imminent).
The fire protection system must detect an incipient fire at the earliest possible stage and activate the acoustic and optical warning devices. In addition it must activate the pre-programmed functions that control the ventilation and some extraction systems. If an automated extinguishing system is present, this must also be activated.
Where an automated extinguishing system has been installed and local regulations require a multiple zone dependency (independent alarm signals across two zones in the same room) before the extinguishing system can be activated, then either an additional high sensitivity smoke detector must be installed.
No standard solution
There is no standard solution for clean room laboratories. Frequently additional fire protection measures are required to further reduce the fire risk to the “accepted” level. The fire risk is the product of the probability of a fire occurring and the consequential damage from that fire. Hence the risk can be lowered either by reducing the probability of fire occurring or by reducing the possible damage. The probability of a fire occurring can be significantly reduced by observing the following recommendations:
The greatest source of risk stems from the people working in the clean rooms. Practice shows that many fires could have been avoided if instructions and safety procedures had been followed. It is therefore absolutely essential that all persons who work in the laboratories are not only trained in self-protection topics, but also in how to combat a fire should an incident occur.
Careful handling of easily flammable material and careful handling of easily flammable materials and careful attention to possible ignition sources such as flames, hot objects, chemical reactions or spontaneous combustion are topics that must be dealt with in user training sessions. Regular monitoring also helps to maintain the awareness level for fire protection issues and make improvements where necessary.
Testing electrical equipment and installations
A wide variety of electrical equipment can be found in a clean room. Most of these pieces of equipment consist of a power supply and electronic components and are therefore potential ignition sources. Defective electrical appliances, extension cables or overloaded multi-way power sockets are further potential ignition sources. To minimise the potential danger from electrical equipment and installations, they must be tested regularly. Defective equipment and installations that do not comply with the specified safety standards must be repaired immediately or taken out of service.
Prevention of explosive atmospheres
Activities involving gases and solvent vapours should only be permitted in fume cupboards with appropriately designed ventilation because of the risk of explosion. If for some reason this is not possible, then the area must be monitored with a gas detection system, This system should control the ventilation according to the gas concentration and trigger a warning before a critical concentration can develop.
The consequences (incurred damage) resulting from a fire can be kept to a minimum through a combination of early fire detection and targeted fire fighting.
Early fire detection
The earlier a fire can be detected, the sooner the corresponding countermeasures can be initiated (e.g removal of power, ventilation control, extinguishing). In this way, any resulting damage can be kept to an absolute minimum.
All persons responsible for supervising the processes must be trained in how to react correctly to any fire related situation that might arise.
A timely warning from an automatic fire detector can only be guaranteed if the detector reacts to the fire phenomena generated (smoke, temperature, heat, radiation, gas) and these reach the detector with sufficient intensity.
Like many environments the organisational measures that you can take are key to the ability for systems to work effectively. Complex systems are not inherently safe and this must be taken into account throughout all fire protection measures, no matter the environment.
Clean rooms need to begin their fire safety measures on the drawing board. The fact they are enclosed and segregated by nature assists us in the application of technology but the organisational controls need to be very strong, especially in regard to the actions taken regarding evacuation.
In short, clean rooms present unique challenges to the fire safety professional. However, like all things related to safety, thorough planning, utilisation of the correct and best available technology, coupled with disciplined organisational measures will result in a well-managed and safe facility that limits the risk of fire and the risk to personnel.
Many thanks to my on site Chemistry team and Siemens for providing guidance and information for this article.