16 May Business continuity & the fire safety challenge
Healthcare, food, microelectronics: how smart a cleanroom is equipped and managed is key to a product’s time-to-market. Meticulously designed cleanroom-related contingency and fire safety plans are critical to protecting staff and to avoiding any kind of disruption in the production process. In particular, the ability to ponder and neutralise all elements and situations that could trigger fire and smoke in the operation of cleanrooms demonstrates a company’s level of resilience. Here regular FME contributor Peter Stephenson, Associate Director, BuroHappold outlines the essential steps towards a proactive and systematic approach to fire and smoke management in high-tech production cleanroom facilities.
The purpose of cleanrooms is to prevent any source of contamination caused by the external environment and atmospheric agents. Once a cleanroom is built, however, chemicals, materials used for scientific purposes, construction or product manufacturing, air conditioning debris, room air, vapour, and people’s movement can contribute to an increased fire hazard and potential for the development of smoke and products of combustion. Above all the accumulation of combustible microscopic particles in dust collection systems contribute to the hidden hazards lurking in cleanrooms.
This can result in flash fires or serious explosion hazards.
Fire events in cleanrooms cause an unexpected business disruption that affects the company’s image and financial health. They can contaminate the process tools, destroy results, products and equipment and culminate in an unrecoverable manufacturing and operational downtime. Consequently, a well thought-out fire safety and fire prevention strategy specially tailored to the requirements in cleanrooms should be integral part of any farsighted contingency plan.
Design insight
Cleanrooms being budget-intensive, mission-critical facilities, their design and construction are to be assigned to qualified engineers who ensure reliable project coordination until completion and, if needed, advisory support during the operational phase. Additional guidance is provided by a number of organisations, among others the Industrial Risk Insurer (IRI), the Factory Mutual (FM) Loss Prevention Datasheets, the National Fire Protection Association (NFPA) Codes and Standards and the Clean Room Insurance Association. They all have been continuously developing the parameters that pave the way for an optimal and safe environment, and, consequently, for the delivery of uncontaminated, high-quality products through the entire supply and production chain.
The ability to create and maintain the best space conditions of humidity, pressure and temperature and to understand how heating, ventilation, and air conditioning interact with each other in a controlled environment determine the design quality, the standard for construction, and ultimately the life cycle costs of a cleanroom over its total operating time.
Smoke, Heat Radiation, Combustion: Fire Safety Assessment with no room for half measures
Fire safety, fire prevention and fire suppression measures are subdivided, among others, into cleanroom fire compartmentation; control of construction materials including interior finishes; automatic and manual fire extinguishing systems; fire detection and alarms; fume exhaust systems; smoke control and the monitoring of electrical systems. However, with regard to cleanrooms this is not enough to ensure the highest possible safety standard for humans and materials in the area.
Another hazardous source for fire development in cleanrooms has been identified in a considerable number of working tools as part of the facility’s operational infrastructure. As a consequence, fire risk assessment in cleanrooms stretches to the entire infrastructure equipment. Although modern working devices are made from inherently fire-safe materials, particular attention is to be paid to the identification of any possible ignition source – from combustion air and silica dust to abrasion particles, chemical dispersion, chromium or nickel compounds.
It has become a routine practice to continuously monitor and ensure the proper handling of flammable liquids, gases and solids in cleanrooms. The same accurate risk assessment is to be equally applied to fire and explosion risks deriving from the use of anti-static plastics for clothing and sheeting or other dangerous substances like lower flash point solvents in conjunction with separate exhaust systems within the cleanroom itself.
Reducing the risk of fire in cleanrooms: where consultants’ experience matters
Early fire detection is possible through approved air sampling and aspirating systems. This early warning enables in-house fire teams to investigate accordingly and, through cause & effect protocols can initiate the fire safety systems – for example by charging a dry pipe sprinkler system with a pre-action mode.
However, a few fire prevention and fire extinguishing agents may help on one side, but can cause serious damage to the infrastructure on the other. As an example, in the UAE sprinklers with spacing and discharge density, as required in the UAE Fire and Life Safety Code and the Standard for the Installation of Sprinkler Systems (NFPA 13), have been a popular choice for cleanroom protection. The potential damage associated with water, heat, steam, and combustion products is considerable as wet systems are reliant on thermal initiation with a potential delay in operation.
Particular fire extinguishing agents can seriously harm the infrastructure, even more than the fire itself, due to the fire suppression agent. Any water-based system could lead to short circuits and cause damage to the electrical components. The deposit of extinguishing media residue deriving from dry powder and foam portable extinguishers can be harmful to the costly and sophisticated technical devices located in the cleanroom. The solution lies in the use of “clean agents” that leave no corrosive or abrasive residues after their use. Clean agents being electrically non-conductive, represent the ideal protection for electronic equipment.
The evolution of fire protection in cleanrooms: atmospheric control
A relatively new fire suppression and fire prevention method is hypoxic air technology – also called atmospheric control technology. The Dubai-based engineering firm, Opsys offers CAP9 which is a unique and reliable fire protection system without any negative impact on assets and property during use. The atmospheric control system is one of the most advanced in this field of operations and is approved by Dubai Civil Defence and certified by UL.
With this progressive technology “made in Dubai”, it’s possible to reduce the ratio of oxygen to nitrogen – in general 1:4 – to a point where the nitrogen begins to exceed the oxygen to a level where the non-reactive particles start to limit the ability of materials to sustain a fire (ratio 1:6).
Standards & guidance
In the United Arab Emirates, guidance on fire protection standards for cleanrooms can be found in the UAE Fire & Life Safety Code, in NFPA’s “318 Standard for the Protection of Semiconductor Fabrication Facilities”, and in “287 Standard Test Methods for Measurement of Flammability of Materials in Cleanrooms Using a Fire Propagation Apparatus (FPA)” – just to name a few.
Despite the massive safety precautions already in place in many cleanrooms, the risk of fire is still severe – the potential dangers are unavoidable.
Accuracy, site-specific, up-to-date knowledge, and experience – these are the key ingredients to design effective measures that limit the generation and spread of fire, smoke and heat radiation in a cleanroom. They determine the safety level of a cleanroom and its level of resilience by increasing operational reliability and providing for extensive investment protection.
BuroHappold Engineering is an international engineering consultancy operating in 23 locations worldwide, with over 50 partners and 1,500 staff including some of the world’s leading consulting engineers. For 40 years we’ve been building our reputation for delivering creative, value led building and city solutions for an ever changing world.