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 can consult OSHA's website at https://www.osha.gov.

May 12, 1988

SUBJECT: Application of 29 CFR 1910.106 and/or NFPA
  30-1987 to Flammable Liquid Storage and Dispensing
  Operations of Polyester Resin

The circumstances of your on-going inspection, as described by your memorandum of March 23, 1988, have been evaluated.

The specific requirements of the standard at 29 CFR 1910.106 need to be tempered by the current guidance of the NFPA 30-1987. This is particularly necessary in instances where polyester resin is involved. As you are aware, increased workplace usage of compounds such as polyester resin have occurred since the earlier adoption of NFPA 30-1969 by OSHA. Furthermore, the issuance of the Haz/Com standard has made available specific handling data now disseminated to all users. Field personnel are therefore advised that reference must be made to the guidance in the current consensus standards and the available safety data sheets when evaluating workplace hazards involving polyester resin.

Response to your questions are presented in the same order as given in your memorandum, and are as follows:

l. 29 CFR 1910.106(h)(4)(i)(b) pertains to fixed above ground tanks. However, applicable provisions of 1910.106(b) also pertain to portable tanks used in unit physical operations. The provisions pertaining to the control of fire due to potential spillage or tank rupture are of concern. Therefore, 1910.106(b) (4) through (7) are partly applicable to portable tanks less than 660 gals in size. (Ref. paragraph 1910.106(h) (4) via 1910.106(e)(3)(vi).)

2. 29 CFR 1910.106(h)(4)(i)(d) applies to both portable containers and portable tanks. Applicable portions of 1910.106(d) must be evaluated relative to the portable tanks observed.

3. Yes

4. & 5. Portions of 1910.106(b) and (d) are applicable as noted in 1 and 2 above.

6. The emergency vent noted by your enclosure (Betts Industries, Inc., 16x10 PAF Manhole) is in compliance 1 since it opens fully at 5 psig to vent 180,000 Cu. Ft. Free Air per Hr. Earlier opening of the vent at 3 psig is acceptable. The functional condition of the vent is of far greater concern. (Ref. to response No. 8, below.)

7. 29 CFR 1910.106 is silent regarding this question. However, various sources suggest appropriate solutions.

(a) The National Safety Council Data Sheet No. 1-627-Rev. 82, paragraph 21, indicates that styrene monomer must be inhibited for shipment and storage. The basic compound is therefore not unstable; however, uninhibited styrene is always present in the vapor form and requires special care. (Refer to paragraph 26-30 of the NSC Data Sheet.)

(b) Should an acceptable sprinkler system be available then an additional factor of safety can be derived if a tank temperature warning device is installed. (Ref. NSC, paragraph 57; also NFPA 30-l987, section 2-2.5.7.)

(c) MSDS by GP No. 351, recommends that unstable liquids be inerted with nitrogen while in storage.

8. NFPA 30-1987, section 2-2.5.4 recommends appropriate venting. A self-closing manhole cover is recommended for use. It should be noted that a vent with a fusible link is not listed. In this case, a fusible link relief device is definitely not advisable, since the material would polymerize and likely explode at temperatures above 150 F. (Ref. VCH Data Sheet No. 1509.)

It is recommended that the care of the relief device conform to the recommendations of MCA (presently CMA) Data Sheet SD-37, paragraph 6.6. The manufacturer (supplier) should be contacted to obtain inspection and cleaning procedures and requirements. Maintaining the functional integrity of the pressure relief device is paramount to the safety of storage and handling of polyester resin. Furthermore, it is imperative that the inhibitor be maintained at an acceptable level. (Ref. MCA Data Sheet, SD-37, paragraph and 5.2.)

9. OSHA Instruction STD 1-5.7 is inapplicable to the subject operations.

10. A portable tank meeting the requirements of DOT Spec 57 is in compliance with 29 CFR 1910.106(d)(2).

The recommendations and requirements of the current NFPA 30-1987 must be considered when evaluating any facility in which polyester resin is stored and used. The NFPA now classifies the unstable component, uninhibited styrene, of polyester resin as a Class 1A liquid. (Ref. NFPA 30-1987, section 4-1.3.) Therefore, all areas in which the liquid is used or stored must be safe for Class 1A liquids since the vent, if activated, would release uninhibited styrene.

Section 2-4.1.1 of NFPA 30-1987 specifies the facility requirements for the handling and storage of flammables at inside locations. It is recommended that these requirements are applicable to the storage and handling of polyester resin in portable tanks.

Section 2-6 of NFPA 30-1987, Source of ignition and 1910.106 (e)(5) through (9) are applicable.

The following reference documents are attached:

1. NFPA 30-1987

2. MCA Chem. Data Sheet SD-37

3. VCH Data Sheet 1509

4. GP Data Sheet No. 351, Rev. B

5. Marson Corp., Data Sheet No. MAR-Glass

6. NSC, Data Sheet 1-627-Rev. 82







March 23, 1988


  Directorate of Compliance Programs
THROUGH: LEO CAREY, DIRECTOR Office of Field Programs
FROM: LINDA R. ANKU Regional Administrator
SUBJECT: Application of 29 CFR 1910.106 to a Flammable Liquid Storage and Dispensing Operation During an ongoing inspection a CSHO encountered a flammable liquid storage and dispensing operation where it was not clear which portions of 29 CFR 1910.106 applied. Due to the complexities of the issues involved and because the determination will impact on operations outside of Region III, this request regarding applicability is being sent to you for your review.

The employer is engaged in a procedure that appears to be a unit physical operation. (For specific details and specifications please refer to the enclosed copy of correspondence dated March 7, from the Allentown District Office of Region III.) The employer is dispensing a Class 1c liquid from a low pressure portable tank (307 gallon capacity--filled with approximately 260 gallons of liquid) that is inside a building. When the tank's contents are depleted the tank is sent back to the supplier to be refilled. This procedure apparently is beneficial to the parties involved in that it eliminates the need to dispose of a container that contained a hazardous material.

The following questions have been posed regarding the applicability of portions of 29 CFR 1910.106:

1. Does paragraph (h)(4)(ii) of 29 CFR 1910.106, which indicates that the storage of flammable and combustible liquids in tanks shall be in accordance with paragraph (b) of 29 CFR 1910.106, which is referenced by paragraph (e)(3)(iv) of 29 CFR 1910.106, apply to portable tanks used in conjunction with unit physical operations?

2. Does paragraph (h)(4)(i)(d) of 29 CFR 1910.106, which references paragraph (d) of 29 CFR 1910.106, apply to both containers and portable tanks or to only containers? This question is posed because the language of paragraph (h)(4)(i)(d) of 29 CFR 1910.106 speaks only of containers but paragraph (d)(2) of 29 CFR 1910.106 speaks of both containers and portable tanks.

3. Do both paragraphs (b) and (d) of 29 CFR 1910.106 apply to portable tanks being utilized in unit physical operations?

4. Is it required that the portable tanks being used, as described in the enclosed attachment, comply with paragraphs (b)(4)(ii); (b)(4)(iii), and (b)(4)(iv)(c) of 29 CFR 1910.106; or

5. are such portable tanks only required to comply with the requirements of paragraph (d) of 29 CFR 1910.106?

6. Is it unsafe that the emergency venting mechanism of the tank is set to open at not less than 3 psig rather than not less than 5 psig?

7. What safety factor in regards to total venting capacity should be required for low pressure tanks containing unstable liquids (i.e., uninhibited styrene component of "polyester" resin)?

8. What type of a safety relief valve should be required for low pressure tanks containing materials (i.e., styrene monomers) that present a potential clogging hazard when polymers may form in the tank vents?

9. Is OSHA Instruction STD 1-5.7 applicable to the operation described in the enclosed attachment?

10. Does the fact that this tank complies with DDT specification 57, Tariff 15 DOT Regulations for Transportation of Hazardous Materials, bring it into compliance with paragraphs (a)(32) and (d)(2) of 29 CFR 1910.106?

Your prompt response to this inquiry would be greatly appreciated since there is an ongoing inspection that cannot be closed until these issues are resolved.

If further information is needed please contact John McFee of my staff at FTS 596-1201.

March 7, 1988


SUBJECT: Storage and Handling of Flammable and Combustible Liquids for Unit Physical Operations in Industrial Plant - 29 CFR 1910.106(e):

was designed in accordance with DOT Spec. #MC3O6.

Your prompt response to these issues would be appreciated in order to expedite the correction of these conditions. Should you have any questions, please contact Walt Siegfried of my staff.

GEORGE J. TOMCHICK, JR. District Supervisor

(Attachments not included)