Although it is not really "new" any longer; OSHA revised 1910.307 in 2007 and many of the facts that are presented in this article may be "news" to a lot of you.  Many of the "new" requirements in 1910.307 Hazardous (classified) Locations are often not well understood or not even known.  This article, which has been extracted from an assortment of OSHA and NFPA documents, will lay out the new and existing requirements of 1910.307  Hazardous (classified) Locations and provide some explanation of the requirements.

The 2000 edition of NFPA 70E contains a number of significant revisions, including a new, alternative method for classifying and installing equipment in Class I Hazardous Locations (HAZLOC).  NFPA has recommended that OSHA revise its general industry electrical standards to reflect the latest edition of NFPA 70E, arguing that such a revision would provide a needed update to the OSHA standards and would better protect employees. This final rule responds to NFPA's recommendations with regard to installation safety in HAZLOCs. It also reflects OSHA's commitment to update its electrical standards, keep them consistent with NFPA standards, and ensure that they appropriately protect employees.  OSHA intends to extend this commitment by using NFPA 70E as a basis for future revisions to its electrical safety-related work practice requirements and new requirements for electrical maintenance and special equipment.

Existing 1910.307 contains OSHA's electrical safety requirements for locations that can be hazardous because of the presence of flammable or combustible substances. HAZLOCs are classified according to the properties of flammable vapors, liquids or gases, or combustible dusts or fibers that may be present. These  locations are designated in the NEC and existing 1910.307 as one of six (6) types:

• Class I, Division 1
• Class I, Division 2
• Class II, Division 1
• Class II, Division 2
• Class III, Division 1
• Class III, Division 2

This system is called the "division classification system," or the "division system." The National Electric Code (NEC) first addressed this system in 1920!

The 2000 edition of NFPA 70E incorporates an alternative system (in addition to the division classification system) for installing electric equipment in Class I locations. (Class II locations continue under the division system.) This system is called the "zone classification system," or the "zone system." The zone system designates three (3) classifications:

• Class I, Zone 0;
• Class I, Zone 1; and
• Class I, Zone 2.

The zone system is based on various European standards that were developed by the International Electrotechnical Commission (IEC).  A modified version of this system was first adopted into the 1996 edition of the NEC. Although the zone and division classification systems differ in concept, individual equipment CAN BE APPROVED for use under BOTH systems when the equipment incorporates protective techniques for BOTH systems (as determined by the nationally recognized testing laboratory that lists or labels the equipment). Based on the successful use of the zone system in European countries for many years and the acceptance of the zone system by the NEC and international standards, OSHA believes that an installation conforming to requirements for this system is as safe as one conforming to requirements for the "division system".

The zone system incorporated in 1910.307 is an ALTERNATIVE method to the division system.  Employers may use either system for installations of electric equipment in Class I HAZLOC. OSHA will recognize the use of the zone system under 1910.307 and any other OSHA standard that references 1910.307.  

Documenting HAZLOCs

OSHA is now requiring employers to document the designation of hazardous locations within their facilities (1910.307(b)). The documentation MUST denote the boundaries of each division or zone so that employees who install, inspect, maintain, or operate equipment in these areas will be able to determine whether the equipment is safe for the location. OSHA is requiring documentation for the division system ONLY FOR NEW INSTALLATIONS that use this HAZLOC designation system. The document requirement does apply, however, to ALL INSTALLATIONS MADE UNDER THE ZONE SYSTEM.

1910.307(b) Documentation. All areas designated as hazardous (classified) locations under the Class and Zone system and areas designated under the Class and Division system established after August 13, 2007 shall be properly documented. This documentation shall be available to those authorized to design, install, inspect, maintain, or operate electric equipment at the location.

This requirement would ensure that the employer has records of the extent and classification of each such area. The documentation will help employers to determine what type of equipment is needed in these locations and will inform employees of the need for special care in the maintenance of the electric equipment installed there. OSHA carefully considered the need to document these areas and tried to balance this need with the extensive burden that would be placed on employers who would have to survey and document their existing hazardous locations. The current standard's division classification system has been in place for many years, and most employers and inspection authorities are familiar with the boundaries for Class I, II, and III, Division 1 and 2 locations. OSHA believes that the benefit of documenting existing hazardous locations installed using the division classification system would be minimal. Therefore, for employers using the division system, OSHA is requiring documentation of boundaries ONLY FOR NEW installations made AFTER August 13, 2007. Employers are NOT required to document existing division-classified systems.  On the other hand, the zone classification system is relatively new. Most employers are not familiar with this system and have little experience determining how to draw the boundaries between the three zones. Relatively few NFPA or industry standards provide specifications for placing those boundaries. Furthermore, the existing OSHA electrical standard recognizes ONLY installations made in accordance with the division classification system, NOT the zone classification system. Any existing installation made under the zone system is technically out of compliance with OSHA's existing standard. However, because the NEC represents standard industry practice, existing zone system installations will almost certainly have been installed in accordance with an edition of the NEC that recognizes the zone classification system (the 1999 and 2002 editions). These editions of the NEC EXPLICITY REQUIRE documentation of hazardous locations. Thus, an employer with an existing installation made under the zone classification system should already have the documentation required by 1910.307(b). For these reasons, OSHA is applying the documentation requirement to ALL HAZARDOUS LOCATION INSTALLATIONS MADE UNDER THE ZONE CLASSIFICATION SYSTEM. This will provide employers, employees, and OSHA with information critical for determining which equipment is suitable in a given hazardous location.  The NEW requirements pertaining to zone classification in 1910.307(g) provide employers with an alternative installation method that the current standard does not permit. Thus, applying these provisions to older installations would give employers greater flexibility without imposing any new costs. Furthermore, to the extent that employers are already using the zone classification system, those employers are likely already meeting 1910.307(g), which is based on provisions in the 1999 and 2002 editions of the NEC.

OSHA is also adding a new paragraph, 1910.307(f), that lists specific protection techniques under the division system. Neither the current Subpart S nor NFPA 70E explicitly list particular protection techniques that can be used in the division classification system; however, the NEC does provide specific protection techniques for installations made under the division classification system in various requirements throughout the Articles covering hazardous locations. OSHA has listed these techniques in 1910.307(f) to make the standard easier to use and to provide parallel requirements for both the division classification system and the zone classification system.  Protective techniques other than those listed in final paragraph (f) are acceptable if the equipment is:

1. Intrinsically safe as specified in 1910.307(c)(1);
2. approved for the specific hazardous location as specified in 1910.307(c)(2); or
3. of a type and design that the employer demonstrates is safe for the specific hazardous location as specified in 1910.307(c)(3).

New paragraph (f) is intended to clarify the existing OSHA requirements for HAZLOCs by EXPLICITLY listing the types of protective techniques that can be used under the "division classification" system. The protection techniques are required implicitly under the existing standard through the requirements for approval and listing or labeling by a nationally recognized testing laboratory and through the reference to the NEC in the note following existing 1910.307(c)(3).

Brief background and description of the zone system

The zone system stemmed from the independent efforts of countries in Europe and elsewhere to develop an area classification system to address safety in locations containing hazardous substances. The IEC formalized these efforts into the zone system, which is now used to classify the majority of the world's hazardous location systems.  Article 505 of the 1996 NEC included requirements for the U.S. version of the zone system for the first time. The 2000 edition of NFPA 70E includes requirements for the zone system based on the 1999 version of the NEC. OSHA is adopting zone system rules that are based on these NFPA 70E provisions. This will permit electric equipment approved for use in HAZLOCs to be used in U.S. workplaces, under either the division or zone system.

Major differences between the division classification system and the zone classification system

The zone system can best be described by comparing it with the division system. Both systems characterize locations by the likelihood and circumstances under which flammable gases or vapors exist. The systems both define the types of gases or vapors that may exist and categorize them under a number of groups. Each system specifies an allowable range of operating temperature, and corresponding requirements, for electric equipment used in a particular division or zone.

In contrast to the division system, however, the zone system is ONLY used to classify areas that are hazardous because of the presence of flammable gases or vapors (Class I locations). The division system must be used to classify areas that may contain combustible dusts or easily ignitable fibers or flyings (Class II and III locations, respectively).

The zone system defines three types of Class I locations (Zones 0, 1, and 2) rather than two (2) locations under the division system (Divisions 1 and 2).

• Zones 0 and 1 equate to Division 1, whereas Zone 2 equates to Division 2.
• In a Class I, Division 1 location, flammable gases or vapors are or may be present in the air in ignitable concentrations.
• In a Class I, Zone 1 location, ignitable concentrations of flammable gases or vapors are not always present, but such concentrations may exist periodically even under normal conditions.
• By contrast, in a Class I, Zone 0 location, such gases or vapors are present either continuously or for long periods.  Thus, a Class I, Zone 0 location is, in essence, a worst-case Class I, Division 1 location.

Each system classifies flammable gases and vapors into a number of groups. The division system has four (4) such groups, designated A, B, C, and D, with group A containing the most volatile substances, and groups B, C, and D containing gases or vapors that are progressively less volatile. The zone system has three (3) such groups, designated IIA, IIB, and IIC, with group IIC containing the MOST volatile gases, and groups IIA and II B containing gases or vapors that are progressively less volatile. Substances classified under groups A and B in the division system generally fall under group IIC of the zone system. However, some differences exist between the groups in the two systems. Thus, regardless of the classification system being used, equipment intended for use in a Class I hazardous location MUST indicate the groups for which it is approved, as required by 1910.307(c)(2)(ii) and (g)(5)(ii).  Table 2 below summarizes the similarities and differences between the two systems.

The other major differences concern the allowable protection schemes and the maximum allowable surface temperature of equipment under each system. According to the NEC, equipment is acceptable for a hazardous location only if its surface temperatures will NOT approach the IGNITION TEMPERATURE, or more specifically the autoignition temperature, of the particular gases and vapors that might be present in that location. There are 14 temperature limits, and corresponding identification codes, under the division system. Each limit specifies the maximum surface temperature for equipment labeled with the matching code. There are six (6) such temperature limits and corresponding identification codes under the zone system. The six zone system limits correspond directly to 6 of the 14 division system temperature limits. However, the remaining eight division temperature limits have values intermediate to the six zone system temperature limits. Equipment approved for one of these intermediate values may be used under the zone system only for the higher (in temperature) of the two closest zone system values. 

Rationale for adopting the zone system requirements

As stated earlier, the zone system has been accepted in many countries. Such international acceptance has meant that U.S. manufacturers of electric equipment suitable for installation in hazardous locations have had to ensure that their equipment met the zone system requirements if they wished to sell such equipment in zone-system countries in addition to meeting the U.S. division system requirements. Also, U.S. employers that had hazardous locations in their workplaces have sought to use equipment approved for use only in zone-classified locations in this country. This, in turn, led NFPA to incorporate the zone system in the NEC starting in the 1996 edition.

OSHA has determined that employees can be protected from the hazards of explosion in Class I hazardous locations by the installation of electric equipment following the latest NEC requirements for the zone classification system (Article 505 of the 2002 NEC). Therefore, OSHA is incorporating the zone system in this revision of the electrical installation requirements in Subpart S. Under the final standard, employers are able to comply with either the zone classification system or the division system for Class 1 hazardous locations.

Paragraph (g) is entirely NEW

In the final rule, OSHA is adding a new paragraph 1910.307(g) that covers the zone classification system. This new paragraph addresses the following topics related to the zone classification system: scope; location and general requirements; protection techniques; special precaution; and listing and marking. A brief description of the contents of each paragraph follows.

Paragraph (g)(1) permits employers to use the zone classification system as an alternative to the division classification system. As explained in paragraph (a)(4), the requirements in 1910.307 that are specific to installations built under the division classification do not apply to installations built under the zone classification system. Thus, paragraph (c), electrical installations; paragraph (d), conduits; paragraph (e), equipment in Division 2 locations; and paragraph (f), protection techniques do NOT apply to installations built under the zone system.

1910.307(g)(1) Employers may use the zone classification system as an alternative to the division classification system for electric and electronic equipment and wiring for all voltage in Class I, Zone 0, Zone 1, and Zone 2 hazardous (classified) locations where fire or explosion hazards may exist due to flammable gases, vapors, or liquids.

Paragraphs (g)(2)(i) and (g)(2)(ii) describe how hazardous locations are classified under the zone system. The employer must consider each individual room, section, or area separately and must designate locations according to the specific properties of the flammable gases, liquids, or vapors that might be present. The same requirements apply to the division system. 

1910.307(g)(2)(i) Locations shall be classified depending on the properties of the flammable vapors, liquids, or gases that may be present and the likelihood that a flammable or combustible concentration or quantity is present. Where pyrophoric materials are the only materials used or handled, these locations need not be classified.

1910.307(g)(2)(ii) Each room, section, or area shall be considered individually in determining its classification.

Paragraphs (g)(2)(iii) and (g)(2)(iv) require that conduit threads be of certain types and that connections be made wrench tight. These provisions ensure that there is no arcing across conduit connections in the event that they have to carry fault current. Paragraph (d) contains similar requirements for division system installations.

1910.307(g)(2)(iii) All threaded conduit shall be threaded with an NPT (National (American) Standard Pipe Taper) standard conduit cutting die that provides 3/4-in. taper per foot. The conduit shall be made wrench tight to prevent sparking when fault current flows through the conduit system and to ensure the explosionproof or flameproof integrity of the conduit system where applicable.
1910.307(g)(2)(iv) Equipment provided with threaded entries for field wiring connection shall be installed in accordance with paragraph (g)(2)(iv)(A) or (g)(2)(iv)(B) of this section.
1910.307(g)(2)(iv)(A) For equipment provided with threaded entries for NPT threaded conduit or fittings, listed conduit, conduit fittings, or cable fittings shall be used.
1910.307(g)(2)(iv)(B) For equipment with metric threaded entries, such entries shall be identified as being metric, or listed adaptors to permit connection to conduit of NPT-threaded fittings shall be provided with the equipment. Adapters shall be used for connection to conduit or NPT-threaded fittings.

Paragraph (g)(3) presents the protection techniques that are acceptable in zone-classified hazardous locations. Electric equipment in these locations must incorporate at least one of these protection techniques, and the equipment must be approved for the specific hazardous location. The protection techniques listed in final Sec. 1910.307(g)(3) have been taken directly from NFPA 70E-2000.

1910.307(g)(3) Protection techniques. One or more of the following protection techniques shall be used for electric and electronic equipment in hazardous (classified) locations classified under the zone classification system.
1910.307(g)(3)(i) Flameproof "d" -- This protection technique is permitted for equipment in the Class I, Zone 1 locations for which it is approved.
1910.307(g)(3)(ii) Purged and pressurized -- This protection technique is permitted for equipment in the Class I, Zone 1 or Zone 2 locations for which it is approved.
1910.307(g)(3)(iii) Intrinsic safety -- This protection technique is permitted for equipment in the Class I, Zone 0 or Zone 1 locations for which it is approved.
1910.307(g)(3)(iv) Type of protection "n" -- This protection technique is permitted for equipment in the Class I, Zone 2 locations for which it is approved. Type of protection "n" is further subdivided into nA, nC, and nR.
1910.307(g)(3)(v) Oil Immersion "o" -- This protection technique is permitted for equipment in the Class I, Zone 1 locations for which it is approved.
1910.307(g)(3)(vi) Increased safety "e" -- This protection technique is permitted for equipment in the Class I, Zone 1 locations for which it is approved.
1910.307(g)(3)(vii) Encapsulation "m" -- This protection technique is permitted for equipment in the Class I, Zone 1 locations for which it is approved.
1910.307(g)(3)(viii) Powder Filling "q" -- This protection technique is permitted for equipment in the Class I, Zone 1 locations for which it is approved.

Paragraph (g)(4) sets special precautions that must be taken with respect to hazardous locations classified under the zone system. First, the CLASSIFICATIONS of AREAS and the SELECTION OF EQUIPMENT AND WIRING MUST BE UNDER THE SUPERVISION of a qualified registered professional engineer (P.E.). This provision is contained in NFPA 70E-2000 and in the 1999 NEC. Because the zone system has been permitted in the U.S. only since 1997, employers and installers in this country have had relatively little experience with installations made using the zone classification system. The technical committees that developed NFPA 70E and the NEC have determined that, for the zone system, it is ESSENTIAL FOR COMPETENT PERSONS to classify the hazardous locations and select equipment for those locations. OSHA agrees with the consensus determination by these committees, which are composed of members (such as NRTLs, electric equipment manufacturers, electrical contractors, and affected employee organizations) with expertise in electrical safety in hazardous locations.  Paragraph (g)(4) requires the services of a qualified registered professional engineer to ensure that the person primarily responsible for the design of the installation is particularly suited to the task. A registered professional engineer who does NOT have an understanding of the construction and operation of the equipment and the hazards involved in zone-classified locations would NOT meet the criteria spelled out in 1910.307(g)(4) and in the definition of "qualified person." The NEC requirements for installations made under the "division classification" system, on the other hand, are far more detailed and are more specification oriented. Because the division system has been in existence in this country for so long, because electricians and safety professionals have had decades to become familiar with it, and because (as noted earlier) many consensus standards specifically delineate the boundaries of locations classified under the division system, it is much easier for an electrician or a safety professional with a strong electrical background to properly classify a hazardous location under the division classification system. Furthermore, because the NEC division-system requirements are so detailed, it is easy for an electrician or a safety professional to select equipment appropriate for such a location. It is considerably more difficult to perform those same duties under the zone classification system. Paragraph (g)(4) also indicates when it is safe to have locations classified using the division system on the same premises as locations classified under the zone system and vice versa. These provisions are also taken from NFPA 70E-2000.

1910.307(g)(4) Special precaution. Paragraph (g) of this section requires equipment construction and installation that will ensure safe performance under conditions of proper use and maintenance.
1910.307(g)(4)(i) Classification of areas and selection of equipment and wiring methods shall be under the supervision of a qualified registered professional engineer.
1910.307(g)(4)(ii) In instances of areas within the same facility classified separately, Class I, Zone 2 locations may abut, but not overlap, Class I, Division 2 locations. Class I, Zone 0 or Zone 1 locations may not abut Class I, Division 1 or Division 2 locations.
1910.307(g)(4)(iii) A Class I, Division 1 or Division 2 location may be reclassified as a Class I, Zone 0, Zone 1, or Zone 2 location only if all of the space that is classified because of a single flammable gas or vapor source is reclassified.
Note to paragraph (g)(4) of this section: Low ambient conditions require special consideration. Electric equipment depending on the protection techniques described by paragraph (g)(3)(i) of this section may not be suitable for use at temperatures lower than -20 ºC (-4 ºF) unless they are approved for use at lower temperatures. However, at low ambient temperatures, flammable concentrations of vapors may not exist in a location classified Class I, Zone 0, 1, or 2 at normal ambient temperature.

Paragraph (g)(5) contains requirements for marking equipment that is approved for hazardous locations classified under the zone system. These provisions are comparable to the corresponding marking requirements under the division system, but reflect the need to provide information necessary for safely installing equipment in a zone-classified location. As noted earlier, paragraph (g)(5)(ii)(C) contains an exception for equipment that the employer demonstrates will provide protection from the hazards arising from the flammability of the vapors, liquids, or gasses involved AND that will be RECOGINIZED AS SUCH by employees. Equivalence of systems and permitted protection techniques. A given area classified under one system is NOT permitted to overlap an area classified under the other system. For example, although Division 2 and Zone 2 are basically equivalent classifications, under the final standard a Zone 2 location is permitted to touch a Division 2 location, but the two locations are NOT permitted to overlap. This ensures that equipment installed and maintenance performed in these locations are appropriate for the conditions in each location.

1910.307(g)(5) Listing and marking.
1910.307(g)(5)(i) Equipment that is listed for a Zone 0 location may be installed in a Zone 1 or Zone 2 location of the same gas or vapor. Equipment that is listed for a Zone 1 location may be installed in a Zone 2 location of the same gas or vapor.
1910.307(g)(5)(ii) Equipment shall be marked in accordance with paragraph (g)(5)(ii)(A) and (g)(5)(ii)(B) of this section, except as provided in (g)(5)(ii)(C).
1910.307(g)(5)(ii)(A) Equipment approved for Class I, Division 1 or Class 1, Division 2 shall, in addition to being marked in accordance with (c)(2)(ii), be marked with the following:
1910.307(g)(5)(ii)(A)(1) Class I, Zone 1 or Class I, Zone 2 (as applicable);
1910.307(g)(5)(ii)(A)(2) Applicable gas classification groups; and
1910.307(g)(5)(ii)(A)(3) Temperature classification; or
1910.307(g)(5)(ii)(B) Equipment meeting one or more of the protection techniques described in paragraph (g)(3) of this section shall be marked with the following in the order shown:
1910.307(g)(5)(ii)(B)(1) Class, except for intrinsically safe apparatus;
1910.307(g)(5)(ii)(B)(2) Zone, except for intrinsically safe apparatus;
1910.307(g)(5)(ii)(B)(3) Symbol "AEx;"
1910.307(g)(5)(ii)(B)(4) Protection techniques;
1910.307(g)(5)(ii)(B)(5) Applicable gas classification groups; and
1910.307(g)(5)(ii)(B)(6) Temperature classification, except for intrinsically safe apparatus.

Note to paragraph (g)(5)(ii)(B) of this section: An example of such a required marking is "Class I, Zone 0, AEx ia IIC T6." See Figure S-1 for an explanation of this marking.

1910.307(g)(5)(ii)(C) Equipment that the employer demonstrates will provide protection from the hazards arising from the flammability of the gas or vapor and the zone of location involved and will be recognized as providing such protection by employees need not be marked.

Note to paragraph (g)(5)(ii)(C) of this section: The National Electrical Code, NFPA 70, contains guidelines for determining the type and design of equipment and installations that will meet this provision.

Notes to Table 2:
\1\ Use of the equivalence shown in the table above must be done only as permitted by Sec.   1910.307.
\2\ The zone classification system described in this preamble does not cover Class II or Class III locations.
\3\ See the discussion of maximum allowable surface temperatures earlier  in the preamble.

Table 3 describes which protection techniques may be used in which classified locations.

Listing and labeling by Nationally Recognized Testing Labratories (NRTLs)

1910.303(a) continues the existing requirement that all electric equipment be approved. While OSHA believes that approval is necessary for all electric equipment, the need for third-party approval of electric equipment in hazardous locations is particularly CRUCIAL. The techniques for ensuring safety in hazardous locations require careful manufacturing and testing of products because tolerances are tight and the margin for error is slim. Thus, OSHA's general industry electrical installation standard has always called for equipment approval, which generally requires listing or labeling by a nationally recognized testing laboratory (NRTL) of equipment installed in hazardous locations.  Under 1910.7, OSHA recognizes testing organizations that are capable of performing third-party testing for safety and designates them as NRTLs. Employers may use products listed by NRTLs to meet OSHA standards that require testing and certification. NRTLs test and certify equipment to demonstrate conformance to appropriate test standards. Many of these test standards cover equipment used in hazardous locations.  Equipment that is of a type that no nationally recognized testing laboratory accepts as being safe can achieve approval through acceptance by a Federal, State, or local authority having jurisdiction over the safety of electrical installations. Custom-made equipment can gain approval through testing by the equipment manufacturer. However, these two modes of approval are rare for equipment installed in hazardous locations. Federal, State, and local authorities generally look to NRTLs for equipment approval, and this is even more true for equipment installed in hazardous locations. This type of equipment must be tested to ensure that it is safe, and these authorities generally do not have the capability to do electrical testing. Custom-made equipment, by its nature, is very rare. Existing 1910.307(b) also recognizes equipment that is "safe for the hazardous (classified) location." This provision permits equipment that is approved for installation in nonhazardous locations if the employer demonstrates that the equipment will provide protection from the hazards arising from the combustibility and flammability of vapors, liquids, gases, dusts, or fibers. This condition exists ONLY IN LIMITED CIRCUMSTANCES as demonstrated by the 2002 NEC, which permits only certain types of general-purpose equipment in hazardous locations and then only under limited conditions. For example, Section 501.8(B) of the 2002 NEC permits nonexplosionproof enclosed motors in Class I, Division 2 locations if they have no brushes, switching mechanisms, or similar arc-producing devices and if exposed motor surfaces do not exceed 80 percent of the ignition temperature of the gas or vapor involved.

OSHA's existing requirements for hazardous locations in Subpart S ONLY address locations classified under the division system, and NRTLs perform testing based on that system. However, test standards currently used by NRTLs to test equipment in hazardous locations classified by division are NOT AUTOMATICALLY appropriate for testing such equipment for use under the zone system. These current test standards are based on protective techniques used for equipment designed for use under the division system and do not contain criteria for protective techniques used in the zone system. Electric equipment that has been approved by an NRTL for use in division-classified hazardous locations may be capable of igniting flammable gases or vapors when used inappropriately in zone-classified locations. Such hazardous equipment can cause a catastrophic explosion and the deaths of and injuries to many employees. In recognizing laboratories under 1910.7 to test products designed for installation in zone-classified locations, OSHA will ensure that the proper test standards are used and look closely at the capability of the laboratory to perform testing under those standards.