December 26, 2007

Mr. John C. Lewis
Process Discipline Leader
O'Neal Engineering, Inc.
3000 RDU Center Drive, Suite 200
Morrisville, NC 27560

Dear Mr. Lewis:

Thank you for requesting clarification of the Occupational Safety and Health Administration (OSHA) standard, 29 CFR 1910.106, pertaining to storage and use of flammable and/or combustible liquids. This letter constitutes OSHA's interpretation only of the requirements discussed, and may not be applicable to any questions not delineated within your original correspondence. We apologize for the delay in our response. Your paraphrased scenario and questions, and our responses are provided below.

Scenario:Typically, the flammable liquid usage in pharmaceutical manufacturing operations involves Isopropyl Alcohol or Ethanol for chromatography column regeneration and buffer preparation. These are Class IB and Class IC flammable liquids. The chromatography operations are in-line with the production process. These chromatography operations may fall under §1910.106(e).

Question 1: In a manufacturing plant where small quantities of flammable liquid(s) are used in a manufacturing process (i.e., less than ten gallons of Class IC liquid), is this considered as incidental storage/or use as discussed in 1910.106(e)(2)?

Response 1: No. Since the chromatography operation, as you noted in your scenario, is part of a production process (i.e., in-line with production process), §§1910.106(e)(3), 1910.106(h), and 1910.119 may apply.

Question 2: §1910.106(e)(2)(iii) in part states that "Adequate natural or mechanical ventilation shall be provided." Does the adequate ventilation in this paragraph mean the ventilation rate of 1 cubic foot per square foot of solid floor area, as defined in §1910.106(e)(3)(v)?

Response 2: As defined in §1910.106(a), ventilation is "considered to be adequate if it is sufficient to prevent accumulation of significant quantities of vapor-air mixtures in concentrations over one-fourth of the lower flammable limit." However, if an employer chooses to provide a ventilation of 1 cubic foot per minute per square foot of solid floor area, as required under 1910.106(e)(3)(v), OSHA would consider such a rate to meet §1910.106(e)(2)(iii) requirements. You must note, however, that compliance with §1910.106 requirements may not preclude an employer from complying with other OSHA standards, such as §1910.1000 (which has requirements pertaining to health hazards). Compliance with §1910.1000 may require ventilation rates higher than the rates prescribed under §1910.106.

Question 3: Does §1910.106(e)(2)(iii) require introduction of fresh air similar to provisions contained in §1910.106(e)(3)(v)(a)?

Response 3: No. §1910.106(e)(2)(iii) does not require the exclusive use of fresh air for ventilation purposes. Additionally, 1910.106(e)(2)(iii) is a performance requirement and does not explicitly require introduction of fresh air to meet the performance requirements of the standard. OSHA, under §1910.106(e)(2)(iii), expects employers to provide adequate ventilation to maintain concentrations below 25% of the LEL. In other words, if an employer covered under §1910.106(e)(2)(iii) chooses to recirculate air, then the employer must take measures to provide adequate ventilation to maintain concentrations below 25% of the LEL.

Note that the recirculation of air for ventilation purposes can result in the reintroduction of already exhausted flammable and combustible materials back to the ventilated area. This recirculation can result in a buildup of flammable and combustible materials in the area being ventilated to rise to concentrations which are considered dangerous, i.e., greater than the 25% of the LEL. Paragraph 17.11 of NFPA 30-2008, which is applicable to all operations, including those at industrial plants, contains requirements for mechanical and natural exhaust ventilation. This paragraph requires exhaust ventilation to discharge to a safe location outside the building. In addition, this section prohibits the recirculation of the exhaust air with exception:

17.11.6 Recirculation of the exhaust air shall be permitted only when it is monitored continuously using a fail-safe system that is designed to automatically sound an alarm, stop recirculation, and provide full exhaust to the outside in the event that vapor-air mixtures in concentrations over one-fourth of the lower flammable limit are detected.

Therefore, although §1910.106(e)(2)(iii) does not explicitly require fresh air to prevent the short circuiting of the ventilation, when recirculated air is used, OSHA expects the controls listed in NFPA 30-2008 paragraph 17.11.6 to be used to control a potential fire/explosion hazard that could seriously or fatally injure employees. OSHA may find that the failure to do so constitutes a violation of the General Duty Clause of the OSHAct (29 USC §654(a)(1)).

Question 4: Does §1910.106(b) apply to storage of Class IB or IC flammable liquids in quantities less than 120 gallons?

Response 4: §1910.106(b) applies to fixed tanks, regardless of quantities involved; it does not apply to drums, containers, or portable tanks. If quantities less than 120 gallons of Class IB or IC are stored (i.e., not used in a process/process tank or not staged in a process area ready to be used) in fixed tanks, then §1910.106(b) will apply.

Question 5: Regardless of quantity, does §1910.106(e)(2)(iv)(d), §1910.106(h)(4)(iii)(a), or §1910.106(h)(4)(iv)(a) prohibit pouring of a Class IB liquid into the open manway of a buffer tank in making a Class IC liquid?

Response 5: There is insufficient information provided to determine if the plant is an industrial (covered under 1910.106 (e)) or a processing plant (covered under 1910.106(h)). Further, if this question were related to an industrial plant, due to the lack of information, we cannot determine which of the industrial plant requirements would apply ((e)(2) – Incidental storage or (e)(3) – Unit Physical Operations). However, we have provided information below, which may assist you in determining how to apply the various standards in question.

If the operation is an incidental activity covered by §1910.106(e)(2), paragraph §1910.106(e)(2)(iv)(d) allows transfer of flammable or combustible liquids into vessels, containers and portable tanks within a building only:

a) through a closed piping; or
b) from safety cans; or
c) by means of a device drawing through the top; or
d) from a container or portable tanks by gravity through an approved self-closing valve.

Therefore, pouring (i.e., one means of gravity transfer) flammable and combustible liquids into an open manway of a process tank/vessel would be allowed (for operations covered under 1910.106(e)(2)) per the language of the standard, "from safety cans" or "from a container or portable tanks by gravity through an approved self-closing valve." However, during such a pouring operation (as stated in the question), the employer must take measures for protection against static sparks (see §1910.106(e)(6)(i)), through bonding and grounding methodologies, e.g., by electrically interconnecting the transfer nozzle of the pouring container and the tank and by ascertaining that the receiving tank is grounded to dissipate any potential static current that may have generated during the pouring operation.

However, if the operation in question is part of a unit physical operation covered under §1910.106(e)(3), then §1910.106(e)(3)(vi) (which refers to §1910.106(h)(4)), indirectly prohibits the use of gravity flow, except as required in process equipment. See §1910.106(h)(4)(iii)(a). If an employer claims this exception, versus providing pumps or water displacement for transfer through piping, as required under this paragraph, they must be prepared to demonstrate why the process equipment necessitates gravity flow through piping in lieu of the pumping. In either case, whether the transfer is by means of gravity flow or by means of a pump, open-pouring of large quantities flammable or combustible liquids (which will not involve piping) into tanks will be in violation of §1910.106(h)(4)(iii)(a). Section 1910.106(h)(4)(iii)(a)'s requirement for pumps or water displacement comes from NFPA 30-1969, which was adopted in 1971 by OSHA into 1910.106. In commentary on this requirement, the NFPA stated that it was intended to prohibit transfer by pouring in such circumstances.¹

Additionally, if the operation in question is part of a processing plant covered by §1910.106(h), as stated above, §1910.106(h)(4)(iii)(a) prohibits the gravity transfer of large quantities of flammable and combustible liquids into an open manway of a process tank. Since open pouring involves transfer without piping, such pouring will be in violation of §1910.106(h)(4)(iii)(a).

Question 6: Are vents and emergency relief vents on portable tanks containing Class 1B and 1C flammable liquids required to be piped outside the building?

Response 6: OSHA does not have any provisions that require the emergency relief devices on portable tanks to discharge to the outside of buildings. However, if portable tanks are part of a PSM-covered process, at a minimum, the employer would be required to identify, evaluate, and control [§1910.119(e)(1)] the hazard of discharging flammable and combustible materials through an emergency relief device into the inside of a building. If this same condition exists for a non-PSM-covered process and employers have not properly evaluated and controlled a release inside a building or a room from emergency relief devices on portable tanks, the employer may be cited under the General Duty Clause of the OSH Act for not controlling a serious fire/explosion hazard that is likely to cause death or serious physical harm to employees.

Question 7: Does §1910.106(e)(2)(ii)(c) and §1910.106(h)(4)(i)(b) apply to processing tanks, such as a buffer mix tank (not a storage tank)? If not, is there a requirement for the processing tank to vent outside the building?

Response 7: OSHA considers that buffer mix tank operations – where a Class IB liquid is poured into buffer mix tank in making a Class IC liquid – as process tanks, and not storage tanks. OSHA standards §1910.106(e)(2)(ii)(c) and §1910.106(h)(4)(i)(b) apply to storage tanks and not to process tanks, such as buffer mix tanks, and OSHA's 1910.106 standards do not have provisions requiring processing tanks such as mix tanks containing Class I liquids to vent outside the building. This assumes these tanks are not pressure vessels, i.e., designed to operate at pressures greater than 15 psig. If these tanks are pressure vessels, good engineering practice according to the ASME (Section VIII, UG-134(g) of the ASME Boiler and Pressure Vessel Code) requires in part, "Discharge lines from pressure-relieving safety devices shall . . . lead to a safe place of discharge [emphasis added]."

Similar to our Response 6, the employer is responsible for controlling the serious hazard of relieving/venting a process tank into a confined area such as a room/building. If a process tank is part of a PSM-covered process, then the employer must control the hazard as stated in Response 6. If the process tank is not part of a PSM-covered process, and this hazard exists, then OSHA may enforce the General Duty Clause of the Act. Note that NFPA 30 – 2008, Paragraph 17.11 requires that exhaust ventilation be discharged to a safe location outside of buildings. This provision applies to all types of operations that use and handle flammable and combustible liquids. Additionally, section 17.15.3 of NFPA 30-2008, in part, states that "The extent of fire prevention and control that is provided shall be determined by means of an engineering evaluation of the operation and application of sound fire protection and process engineering principles." OSHA may find that process tanks that do not comply with these requirements violate the General Duty Clause.

Question 8: A prevalent belief is that if there is adequate ventilation, processing tank vents do not need to go outside the building. This is desirable in the pharmaceutical industry, because of the concern about the cleanliness of air that may enter the vessel through the vent. Is there a code basis for this belief?

Response 8: As discussed in our Responses 6 and 7 above, OSHA does not have specific standards which prohibit process tanks to vent inside the buildings. However, venting inside a building is prohibited under the OSHA 1910.106 standard for storage tanks containing flammable and/or combustible liquids. 1910.106(b)(4)(ii), which applies to storage tanks inside buildings, in part states that "Vents shall discharge vapors outside the building." In addition, as stated earlier, if process tanks are part of a PSM-covered process, at a minimum, the employer would be required to identify, evaluate, and control [§1910.119(e)(1)] the hazard of discharging flammable and combustible materials through an emergency relief device into the inside of a building. As discussed in our responses above, if employers have not properly evaluated and controlled a release inside a building from process tank vents, OSHA may use section 17.15.3 of NFPA 30-2008 as the basis for enforcing the General Duty Clause for process tanks not venting outside the building for not controlling a serious fire/explosion hazard that is likely to cause death or serious physical harm to employees.

Question 9: Is it acceptable for any tank containing Class I flammable liquids to vent inside the building? If so, what kind of local exhaust pick-up and/or LEL monitoring would be required?

Response: Please see our Responses 6, 7, and 8.

Thank you for your interest in occupational safety and health. We hope you find this information helpful. OSHA requirements are set by statute, standards, and regulations. Our interpretation letters explain these requirements and how they apply to particular circumstances, but they cannot create additional employer obligations. This letter constitutes OSHA's interpretation of the requirements discussed. Note that our enforcement guidance may be affected by changes to OSHA rules. Also, from time to time we update our guidance in response to new information. To keep apprised of such developments, you may consult OSHA's website at http://www.osha.gov. If you have any further questions, please feel free to contact the OSHA Office of General Industry Enforcement at (202) 693-1850.

Sincerely,



Richard E. Fairfax, Director
Directorate of Enforcement Programs

¹ NFPA, Flammable and Combustible Liquids Code Handbook (1^st ed.1981) (commenting on Paragraph 8-4.3.1) [ back to text ]