Safety

Navigating NFPA Codes and Standards Jeremy Lebowitz, P.E. Rolf Jensen & Associates, Inc.

Follow the recommendations and how-to guidance provided by the National Fire Protection Association to safeguard against fires and explosions.

T

he National Fire Protection Association (NFPA) has developed and published more than 300 codes, standards, recommended practices, and guides intended to minimize the possibility and effects of fire and related risks. Virtually every building, process, service, design, and installation in society today is affected by NFPA recommendations. The chemical process industries (CPI) are particularly impacted by the safety measures contained in the NFPA codes and standards. A code is a set of rules put forth as recommendations. It is not a law but can be adopted into law. A standard is a more detailed elaboration of a code, and gives the nuts and bolts of how to follow the code. The NFPA develops codes and standards via a consensus approval process, which requires input from users, code enforcement officials, and special experts. The codes in effect today reflect developments that have taken place over several decades, including lessons learned from tragic events resulting in casualties and/or significant property loss. This article briefly discusses some of the basic NFPA codes and standards that apply to general building design and construction. Then, it explores in more depth the key NFPA documents that apply to chemical processing facilities.

Building-construction standards Many of the NFPA standards are designed as how-to guides to assist property owners and tenants in installing fire protection systems. Typically, the building code of the local jurisdiction dictates which buildings require sprinklers and fire alarms. (The building code may be based on the International Building Code or NFPA 5000, Building Construction and Safety Code). Once it has been determined that a certain fire protection system is required, the appropriate NFPA standard can be consulted to identify 18 

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installation, testing, and maintenance requirements. This section summarizes some of the major NFPA building standards. While chemical engineers generally do not need to deal with these codes and standards, this brief overview can serve as a general reference, as these documents may dictate where and why certain major fire protection systems are required for a given process. Uniform Fire Code (NFPA 1). NFPA 1 is a model fire code that is adopted by fire departments of some jurisdictions (the International Fire Code is adopted in other locations). In jurisdictions that have adopted this code, it is generally enforced by the local fire official. The intent of NFPA 1 is to safeguard life and protect property from fire, explosion, and other dangerous conditions. This code provides valuable guidance on how to protect facilities from the dangers associated with specific hazardous materials, and references many of the other codes and standards discussed in this article. Where adopted, NFPA 1 is often the document that mandates compliance with these other codes and standards. Standard on the Installation of Sprinkler Systems (NFPA 13). This standard explains the nuts and bolts of designing and installing complete sprinkler systems, including guidance on pipe sizing, seismic bracing, and sprinkler selection. Another important parameter covered in NFPA 13 is the quantity of water required to control fires based on the type of chemical involved. For flammable and combustible liquids, NFPA 30 (discussed later) provides more detailed water-flow requirements. National Fire Alarm and Signaling Code (NFPA 72). This document governs the design and installation of fire detection and alarm systems, as well as emergency communications systems (ECS; also commonly referred to as mass notification systems or emergency voice/alarm communication systems). An ECS, a recent addition to NFPA 72, Copyright © 2012 American Institute of Chemical Engineers (AIChE)

Division 1 (5-ft Radius)

Division 2 (10-ft Radius)

Vent

Separator Exhauster Bin

Hot Air

Class I, Division 1

Elevator

Feed Class I, Division 2

p Figure 1. NFPA 70 provides guidance on the use and storage of flammable and combustible liquids in classified locations such as this one. Here, a product dryer handling a solid that is wet with a flammable liquid is located in an adequately vented building.

Flammable and combustible liquids The Flammable and Combustible Liquids Code (NFPA 30) is arguably the most important NFPA code for chemical engineers. The purpose of NFPA 30 is to provide fundamental safeguards for the storage, handling, and use of flammable and combustible liquids. A liquid is considered combustible if it has a flashpoint of 100°F (37.8°C) or higher; flammable liquids are those with a flashpoint below 100°F. The flashpoint is the lowest temperature at which the vapor above the liquid surface is ignitable. Flammable liquids are more hazardous than combustible liquids, because an ignitable vapor concentration can arise above these liquids at temperatures near room temperature. Combustible liquids are less hazardous because significant heating can be required to achieve a concentration that renders the vapor above the liquid ignitable. However, combustible liquids can be just as dangerous as flammable liquids if heated above their flashpoints. Flammable liquids are further categorized based on flashpoints and boiling points into Classes IA, IB, and IC; combustible liquids are categorized by flashpoint into Classes II, IIIA and IIIB (Table 1). Note that the designations for hazardous locations that require classified electrical equipment use similar nomenclature, but area classification is different from the classification of flammable and combustible liquids. NFPA 30 provides specific guidance on how to protect facilities from the hazards associated with flammable and combustible liquids, in containers ranging from pint-sized jars to million-gallon aboveground tanks. NFPA 30 specifies several key protection features for the storage and use of these liquids inside buildings. Size and location of storage rooms. A liquid storage space can be designated a control area, a liquid storage room, or a liquid warehouse, depending on the overall quantity of the liquid stored in it. The amount of liquids that may be housed in each type of space is lowest in control areas and highest in liquid warehouses, as is the stringency of the requirements for protective features. Control areas are rooms, floors, or portions of a building

is extremely valuable for quickly disseminating information to large populations. An ECS can prove immensely beneficial in chemical facilities, especially those that are sparsely populated, and where the installation of traditional fire alarm systems can be cost-prohibitive or could fail to convey sufficient information. National Electrical Code (NFPA 70). The purpose of the National Electrical Code (NEC) is to safeguard people and property from the hazards of electricity. Of principal importance to chemical engineers is Article 500, which discusses electrical and electronic equipment located in classified (hazardous) areas (1). The requirements in Article 500 of the NEC apply to equipment located in areas where flammable vapors (Class I), combustible dusts (Class II), or combustible fibers (Class III) are anticipated, for both Division 1 (the hazard is present during normal, routine operation) and Division 2 (the hazard can occur only during abnormal process conditions, including maintenance). The purpose of this part Table 1. Flammable and combustible liquids can be further divided into classes. of NFPA 70 is to reduce the risk of the Liquid Classification Flashpoint Boiling Point Examples electrical equipment serving as the ignition source for hazardous materials (2). Class IA — Flammable 100°F (37.8°C) All Diesel Fuel, Hydrazine example of a classified location housing >140°F (60°C) All Aniline, Cyclohexanol Class IIIA — Combustible a flammable liquid process. Reference 3 Class IIIB — Combustible >200°F (93°C) All Diethylene Glycol, provides guidance on selecting motors Motor Oil for use in classified areas. Copyright © 2012 American Institute of Chemical Engineers (AIChE)

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that are separated from other control areas and the rest of stored in basements. The rationale for this requirement is the building by fire-resistance-rated construction. Liquids twofold: Heavier-than-air flammable vapors can accumuare heavily restricted in control areas, and as such there are late in pits or sumps and pose a significant hazard to floors no limitations on the size of the room. The amount of flamabove the basement; and, firefighter access is more chalmable and combustible liquids stored or handled in control lenging on floors below grade. This requirement is more areas cannot exceed the specified maximum allowable stringent than the MAQs for below-grade control areas, quantities (MAQs) in Table 2. Note that MAQs also apply which still apply to other classes of hazardous materials. to other classes of hazardous materials, such as oxidizers, (In jurisdictions that enforce the 2006 and later editions of flammable solids, and corrosive materials, through buildthe International Fire Code, small allowances exist for the ing code requirements. The MAQs for hazardous materistorage and use of flammable liquids in basements.) als located on floors above and below Table 2. The amounts of flammable and combustible liquids that can be stored in grade are lower than the MAQs for control areas are restricted based on maximum allowable quantities (MAQs). ground-level spaces, as firefighter access Liquid Class MAQ becomes more difficult (Table 3). 1,2 Flammable Liquids 30 gal (115 L) IA Liquid storage rooms can contain 1,2 1,2 more flammable and combustible liq120 gal (460 L) IB and IC uids than are permitted in control areas. IA, IB, IC (combined)1,2,3 120 gal (460 L) Liquid storage rooms are limited to an 1,2 Combustible Liquids 120 gal (460 L) IIA area of 500 ft2 and must be separated 1,2 IIIA 330 gal (1,265 L) from the rest of the building by fire1,2,4 13,200 gal (50,600 L) IIIB resistance-rated construction (1- or 2-h Notes: fire barriers, depending on room size). 1. Quantities can be increased by 100% if the materials are stored in approved flammable-liquids The MAQs for flammable and combusstorage cabinets or in safety cans in accordance with the fire code. Where Note 2 also applies, the tible liquids do not apply to liquid storincreases can be applied accumulatively. age rooms; rather, flammable and com2. Quantities can be increased by 100% in buildings equipped throughout with an automatic sprinkler system installed in accordance with NFPA 13. Where Note 1 also applies, the increases can be bustible liquid storage may not exceed applied accumulatively. a certain density, which can be up to 10 3. Quantities cannot exceed the maximum allowable quantity per individual control area for Class IA, gal of liquid per square foot of storage Class IB, or Class IC flammable liquids, individually. room area. The maximum allowable 4. Quantities are not limited in a building equipped throughout with an automatic sprinkler system installed in accordance with NFPA 13. densities of flammable and combustible liquids in these areas depend on room size and the presence of automatic fire Table 3. The MAQ for all hazardous materials is reduced for floors above and below grade because firefighter access to those areas is more difficult. suppression systems; densities are lower for smaller rooms and rooms without MAQ per Number of Number of Control Area*, Control Areas Fire-Resistance automatic fire suppression systems. Floors Above or % of GradeAllowed per Rating for Fire Liquid warehouses, unlike the other Below Grade Level MAQ Floor Barriers‡, h designated liquid storage areas, are Above >9 5 1 2 permitted to store unlimited quantities Grade 7–9 5 2 2 of flammable and combustible liquids as long as these areas are substantially 4–6 12.5 2 2 separated from occupiable buildings and 3 50 2 1 property lines (a 4-h-rated fire wall is 2 75 3 1 required if the warehouse is attached to 1 100 4 1 or within 10 ft of another building). LiqBelow 1 75 3 1 uid warehouses are not limited in area. Grade It should be noted that additional build2 50 2 1 ing code requirements apply to liquid >2 NA NA NA storage rooms and liquid warehouses, NA = Not Allowed which are not addressed in this article. * Percentages represent the MAQ per control area shown in NFPA 30, Table 9.6.1, with all of the One notable provision of NFPA 30 increases permitted in the footnotes of that table. ‡ Fire barriers must include floors and walls as necessary to provide a complete separation from that applies to all storage room designations is that flammable liquids cannot be other control areas. 20 

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Copyright © 2012 American Institute of Chemical Engineers (AIChE)

Container and quantity limitations. As noted earlier, MAQs apply to control areas, and storage densities apply to liquid storage rooms. To limit the amount of flammable or combustible liquid that could be involved in a spill, limit­ ations also apply to container sizes. Containers that are brittle or subject to damage under fire conditions (e.g., glass, plastic) are either prohibited for certain materials, or are limited in size. For example, the maximum allowable size of a glass container for a Class IB flammable liquid is 1 quart (1 L), whereas the maximum size for Class IIIA combustible liquids is 5.3 gal (20 L). Approved portable metal tanks and intermediate bulk containers (IBCs) up to 793 gal (3,000 L) may be used to store flammable or combustible liquids in any class. Fire protection system design. NFPA has carried out significant research on the suppression of fires involving flammable and combustible liquids, and the requirements for fire protection systems for the storage of these liquids are highly detailed — above and beyond the scope of NFPA 13. Given the specific nature of these hazards, the prescribed protection criteria are contained in NFPA 30 and referenced by NFPA 13. Sprinkler design criteria are available for numerous storage configurations, including in-rack storage and palletized storage of drums, with protection by ordinary sprinkler systems as well as foam-water suppression systems. Several factors must be taken into account to properly design a sprinkler system for a space where flammable and combustible liquids are stored: • sprinkler system type (water spray or foam-water spray) • container material (metal or nonmetal) • container relief system (relieving or nonrelieving) • miscibility of liquid in water • storage configuration (rack, shelf, stack, or pallet) • details of storage configuration (e.g., for rack storage, single-, double- or multiple-row racks; widths of racks, aisles and flue space width between racks) • storage height • ceiling height • separation between racks or piles. These factors will determine how much water is required from the ceiling (and possibly in-rack) sprinklers, which in turn dictates sprinkler and pipe sizes. Electrical classification. Using electrical equipment that is designated for classified (hazardous) locations is a key measure to reduce the ignition hazards in a facility that handles flammable or combustible liquids. NFPA 30 provides specific guidance for flammable liquid storage and processing areas that require electrically classified equipment. For example, the inside of flammable liquid storage rooms should carry a Class I, Division 2 electrical classification; in rooms that dispense flammable liquids, Class I, Copyright © 2012 American Institute of Chemical Engineers (AIChE)

Division 1 electrically classified equipment should be used within 3 ft of any vent and fill openings. See Ref. 2 for more detailed information on electrical classification and the selection of equipment for use in such areas. Containment, drainage, and spill control. A major concern with flammable and combustible liquid fires is that the pool of burning liquid could spread and involve other containers, possibly initiating a chain reaction. This scenario can quickly overwhelm a facility’s sprinkler system. This threat can be mitigated to some extent with spill control devices, such as berms, curbs, trenches, or spot drains. Spill control is required in facilities utilizing flammable and combustible liquid containers larger than 10 gal. Another concern is that many of these liquids are less dense than water, so the fire suppression water could carry the burning liquid into unaffected areas. Additionally, this runoff could enter public waterways, sewers, or adjoining properties. For these reasons, NFPA requires secondary containment (possibly via an underground tank) and/or drainage to a safe location. Drainage systems should have the capacity to handle the expected discharge rate of fire suppression system water. One way to reduce the size of secondary containment systems is to install a foam-water system, which is designed to suppress — i.e., extinguish — the fire. Traditional sprinkler systems are designed to control a fire, keeping fire growth in check until firefighters respond to extinguish the fire. Hence, water flows and durations required for foamwater suppression systems can be substantially less than a comparable water-only sprinkler system. Explosion control. NFPA 30 requires explosion control where Class IA flammable liquids are stored in containers larger than 1 gal (4 L), due to the higher risk of flammable vapors existing under normal operating conditions. Any of the methods outlined in NFPA 69 (discussed later) can be used for explosion control. Ventilation. Flammable and combustible liquids in storage, and especially in use, can continually liberate flammable vapors. Without sufficient ventilation, these vapors can accumulate to ignitable concentrations. Ventilation should be provided at a minimum rate of 1 cfm per square foot of room area. Equally critical is the location of ventilation supply and exhaust registers — vents should be located within 12 in. of the floor and/or ceiling (depending on whether the expected vapors are heavier or lighter than air), and on opposite sides of the room to promote dilution and removal of flammable vapors.

Laboratory standards The Standard on Fire Protection for Laboratories Using Chemicals (NFPA 45) applies to small facilities such as university laboratories and pilot-scale operations. The primary focus of NFPA 45 is the subdivision of laboratory CEP  May 2012  www.aiche.org/cep 

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buildings into laboratory units, which are classified based on the amounts and relative hazards of the chemicals contained therein. The approach is similar to, and often used in conjunction with, the control area approach outlined in NFPA 30. The requirements of the user (e.g., laboratory researcher, pilot plant engineer, etc.) typically dictate which laboratory unit the facility falls into, ranging from Class A (high fire hazard) to Class D (minimal fire hazard). Table 4 provides specific laboratory unit designations contained in NFPA 45. Many chemical users who handle restricted amounts of flammable and combustible liquids, such as those working in a laboratory or university setting, fall into Class C Laboratory Unit. NFPA 45 details the fire protection features required for each laboratory unit based on its classification. Size limitations, fire-resistance-rated construction, fire protection systems, and even explosion protection systems may be required, depending on the hazard posed by each lab unit. NFPA 45 is particularly valuable when considering ventilation systems for hoods and rooms, as the specific design requirements permit many heating, ventilation, and air conditioning (HVAC) features utilized in “green” building design (e.g., heat recovery, air recirculation, and manifolding) while still providing for a fire-safe exhaust system. Perchloric acid handling presents unique protection challenges because condensed perchloric acid vapors in improperly ventilated areas can form explosive perchlorates; NFPA 45 provides a great deal of guidance for the design of perchloric acid exhaust systems. Finally, NFPA 45 provides specific guidelines for all chemical storage, handling, and waste disposal procedures in laboratories.

Combustible dusts Combustible dusts are present in a range of industries, including pharmaceuticals, chemicals and petrochemicals, grain and food processing, and rubbers and plastics. Despite the potential severity of explosions associated with combustible dusts, many facilities that handle and process such materials are unaware or ill-equipped to deal with the associated hazards (4–7). The remedies described in NFPA 654, Standard for the Prevention of Fire and Dust Explosions from the Manufacturing, Processing, and Handling of Combustible Particulate Solids, are diverse and require a detailed working knowledge of the process to be protected (8). 22 

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Explosion protection should be provided for individual pieces of equipment, and equipment should be isolated to prevent an explosion from propagating to other parts of a plant. Various methods are available for either prevention or mitigation of dust explosions within process equipment. NFPA 654 permits the use of deflagration venting in accordance with NFPA 68, or explosion control via methods such as deflagration suppression systems or oxidant concentration reduction in accordance with NFPA 69 (both of which are discussed in the next section). Deflagration venting is typically necessary for existing combustible-dust processes with indoor dust collectors that do not have explosion protection and that the owner does not want to relocate outdoors. In addition to following the protection methods detailed in NFPA 68 and 69, it is critical to limit a dust explosion to the unit of origin. Efforts to confine an explosion to a single process unit help to reduce the likelihood of perturbations of dust accumulations, and thus a secondary — and usually more devastating — explosion. Several options for isolation of process equipment are available: • chokes. This method isolates the explosion by obstructing flow, thereby leading to the buildup of solid material. The agglomeration of solids within a small cross-sectional area prevents air from passing the fuel — stifling a flame wave at the choke point. Earlier editions of NFPA 69 included screw conveyors as material chokes; however, industry experience has shown that these devices are not reliable as isolation devices. Rotary valves handling solid materials can also function as material chokes. • rotary valves. Rotary valves, which are commonly used on equipment that handles bulk solids (e.g., silos), restrict flow so that a vessel is open at only one end at a time. This prevents an explosion from passing through to

Table 4. The maximum quantities of flammable and combustible liquids that can be stored in a laboratory unit (excluding inside storage areas) are contained in NFPA 45. Lab Unit Fire Hazard Class

Liquid Class

Maximum Quantities in Use

Maximum Quantities in Use and Storage

per 100 ft2, gal

per Lab Unit, gal

per 100 ft2, gal

per Lab Unit, gal

A

I

10

480

20

480

(High)

I, II, IIIA

20

800

40

1,600

B

I

5

300

10

480

(Moderate)

I, II, IIIA

10

400

20

800

C

I

2

150

4

300

(Low)

I, II, IIIA

4

200

8

400

D

I

1

75

2

150

(Minimal)

I, II, IIIA

1

75

2

150

The maximum quantities per 100 ft2 are used to calculate the total quantity allowed per laboratory work area and the total quantity in the laboratory unit. They should not be interpreted as the quantity that can be store in an area of 100 ft2.

Copyright © 2012 American Institute of Chemical Engineers (AIChE)

Product Inlet No Explosion Valve A Rotor Blade

Gap Width

Electrical Interlock

Gap Length Rotor Housing

Valve B Explosion

Rotary Valve

Product Outlet Process Equipment

p Figure 2. When rotary valves are used at both the inlet and outlet of a piece of equipment, they can be electrically tied together so that only one valve can be open at a time. This prevents explosions from traveling upstream.

the equipment upstream. Figure 2 illustrates the schematic configuration and construction of rotary valves. An advantage of this method is that it functions as a passive protection system. • automatic fast-acting valve systems • chemical isolation systems • flame-front diverters The last three methods use inline, automatically actuated systems to prevent an explosion from propagating beyond the process vessel in which it originates. Initiating the fastacting valve or chemical isolation system mechanically or chemically interrupts the flame front, thereby preventing the propagation of the explosion. In the case of the flamefront diverter, the deflagration must reach a preset minimum pressure in order to rupture the valve that directs the ensuing flame front to leave the process piping rather than continue upstream in the process. These methods are Extinguisher generally easier and less expensive to retrofit into an existing process than reconfiguring existing process piping to avoid manifolding.

The Standard on Explosion Protection by Deflagration Venting (NFPA 68) applies to systems that vent combustion gases and pressures resulting from a deflagration within an enclosure so that structural and mechanical damage is minimized. It provides guidelines for safe deflagration venting, including equations to determine vent size, location, and configurations that allow deflagration vents on indoor equipment to safely vent to the building exterior. Detailed design parameters are provided for explosion venting where the hazard is a flammable gas or vapor or a combustible dust. The Standard on Explosion Prevention Systems (NFPA 69) differs from NFPA 68 in that explosion prevention systems address the hazard before the deflagration can progress to an explosion or limit the deflagration to a single process vessel, whereas venting systems simply relieve the pressure generated by a deflagration. NFPA 69 provides methods for the design and approval of deflagration control systems. Oxidant concentration reduction. This method reduces or eliminates the oxidant (typically air) to prevent the formation of an explosive atmosphere within the process equipment, thus preventing a deflagration before it occurs. In a process vessel, the air can be replaced with nitrogen, argon, or another inerting agent, or the oxygen concentration can be reduced to below the lower explosive limit (LEL) for the particular material. Knowledge of the flammability characteristics of the material is needed to use this method (9). Deflagration pressure containment. NFPA 69 allows the use of process equipment that is of sufficiently substantial construction to contain the overpressure associated with a deflagration. However, this can be significantly more expensive than the other means of dust explosion protection discussed here, especially in existing processes. Deflagration suppression systems. This method of explosion protection calls for an active suppression system, rather than one that passively vents or contains a deflagration. As shown in Figure 3, these methods discharge a sup-

Detector

Pressure Wave

Explosion protection NFPA defines deflagration as the propagation of a combustion zone at a velocity that is less than Fireball Ignition Explosion Suppression Suppression Total the speed of sound in the unreacted medium. A Occurs Detected Begins Continues Suppression detonation is a similar phenomenon that occurs at velocities higher than the speed of sound. NFPA Time: 30 msec 80 msec 0 msec 40 msec 20 msec defines an explosion as the bursting or rupturing p Figure 3. The presence of an overpressure wave triggers the discharge of the suppresof an enclosure or a container due to the develop- sant in a deflagration suppression system. The events that occur within a vessel between ignition and full suppression can take about 80 milliseconds. Source: NFPA 654. ment of internal pressure from a deflagration. Copyright © 2012 American Institute of Chemical Engineers (AIChE)

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pressant into the protected vessel or piping when triggered by an overpressure wave caused by deflagration. Dilution with a noncombustible dust to render the mixture noncombustible. In most processes, this method is not appropriate, as dilution with a noncombustible dust would render the combustible dust “product” unusable. This method is also limited in effectiveness due to the high concentrations of inert material required and the potential for separation during handling; other methods are preferred. This method may be appropriate for waste streams (6). Deflagration venting through an approved dustretention and flame-arresting device. Essentially a modified version of deflagration venting, this method provides additional protection by preventing the dust and flame wave from passing the point of the deflagration vent. The dust-retention and flame-arresting device must be approved by a recognized testing laboratory.

Other codes and standards of interest The Standard for Combustible Metals (NFPA 484) contains several chapters detailing protection methods for combustible metals and metal dusts, including alkali metals (e.g., sodium, potassium), aluminum, magnesium, tantalum, and others. Specific processes involving each of the subject metals are discussed, including melting operations, processing and fabrication operations, and scrap storage. Protection from water and moisture is a primary consideration when dealing with combustible metals. In some cases, fire protection systems may consist solely of Class D manual fire extinguishers because the application of water, even from sprinkler systems, is deemed extremely hazardous. The Standard for Spray Application Using Flammable or Combustible Materials (NFPA 33) and the Standard for Dipping, Coating, and Printing Processes Using Flammable or Combustible Liquids (NFPA 34) deal with hazards associated with specific flammable and combustible liquid processes. NFPA 33 focuses on spray applications such as paint booths, while the scope of NFPA 34 is limited to dipping and coating processes. As with other NFPA standards, Jeremy Lebowitz, P.E., works as a consultant for Rolf Jensen & Associates, Inc., a fire-protection engineering consulting firm (Boston, MA; Phone: (508) 620-8900; Email: [email protected]). He has experience designing automatic sprinkler systems and fire alarm systems, and specializes in assisting end users with fire protection requirements for the use and storage of hazardous materials in high-hazard, chemical plant processing and laboratory applications. He has assisted many facilities in developing sprinkler specifications and electrical classification, and designing ventilation, spill containment and drainage, laboratory units, and storage facilities. In addition, he also has experience with hydrogen, compressed natural gas, and combustible dust hazard evaluation, including the recent U.S. Occupational Safety and Health Administration (OSHA) requirements for combustible dusts. He has an MS in fire protection engineering and a BS in chemical engineering, both from Worcester Polytechnic Institute. He is a licensed professional engineer in Massachusetts.

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they include information on electrical ignition sources, and ventilation and storage methods. Static electricity is a primary concern in such facilities. Particular care must be exercised with drying or curing processes, since flammable vapors and heat sources coexist in such environments. NFPA 77, Recommended Practice on Static Electricity, is a very valuable resource for mitigating the hazard of static electricity. NFPA 77 provides tools to assist the user in evaluating and controlling static electricity hazards, including specific guidance for facilities handling flammable and combustible liquids (and their vapors), powders, and dusts. Static electricity is of particular concern where flammable liquids are dispensed or sprayed; bonding and grounding procedures are a primary consideration, in addition to rates of product addition, inerting procedures, and sampling.

Final remarks The NFPA codes and standards contain a wealth of information based on voluminous research and more than a century of experience with fires. Chemical engineers should be aware of the information and recommendations available CEP to help create a fire-safe work environment.

Literature Cited 1. National Fire Protection Association, “National Electrical Code,” NFPA 70, Article 500, Section 500.5, NFPA, Quincy, MA (2011). 2. National Fire Protection Association, “Recommended Practice for the Classification of Flammable Liquids, Gases, or Vapors and of Hazardous (Classified) Locations for Electrical Installations in Chemical Process Areas,” NFPA 497, NFPA, Quincy, MA (2012). 3. van Amerom, U., “Choose the Right Electric Motors for Hazardous Locations,” Chem. Eng. Progress, 107 (11), pp. 18–23 (Nov. 2011). 4. Perry, J., et al., “Addressing Combustible Dust Hazards,” Chem. Eng. Progress, 107 (5), pp. 36–41 (May 2011). 5. Ebadat, V., “Managing Dust Explosion Hazards,” Chem. Eng. Progress, 105 (8), pp. 35–39 (Aug. 2009). 6. Perry, J., et al., “Conducting Process Hazard Analyses for Dust-Handling Operations,” Chem. Eng. Progress, 105 (2), pp. 28–35 (Feb. 2009). 7. Shelley, S., “Preventing Dust Explosions: Are You Doing Enough?,” Chem. Eng. Progress, 104 (3), pp. 8–14 (Mar. 2008). 8. National Fire Protection Association, “Standard for the Prevention of Fire and Dust Explosions from the Manufacturing, Processing, and Handling of Combustible Particulate Solids,” NFPA 654, Section A.7.1.2.1(6), NFPA, Quincy, MA (2006). 9. Crowl, D., “Minimize the Risks of Flammable Materials,” Chem. Eng. Progress, 108 (4), pp. 28–33 (Apr. 2012).

Additional Reading Schram, P., et al., “Electrical Installations in Hazardous Locations,” 3rd ed., NFPA, Quincy, MA (2009).

Copyright © 2012 American Institute of Chemical Engineers (AIChE)