One of the top questions I receive is asking about how NFPA 704 ratings play into the application to OSHA’s Process Safety Management standard and EPA’s Risk Management Plan rule. I hope to clarify any confusion this NFPA 704 application may be causing, as YES – the NFPA 704 does have a role in determining if certain MIXTURES fall under the RMP rule. However, this ONLY applies to certain FLAMMABLE MIXTURES and ONLY is used in EPA’s RMP rule – NOT in OSHA’s PSM application. Let me explain …
EPA makes reference to NFPA 704 in the following manner… (emphasis added by me)
§68.115 Threshold determination.
…
(2) Concentrations of a regulated flammable substance in a mixture.
(i) General provision. If a regulated substance is present in a mixture and the concentration of the substance is below one percent by weight of the mixture, the mixture need not be considered when determining whether more than a threshold quantity of the regulated substance is present at the stationary source. Except as provided in paragraph (b)(2) (ii) and (iii) of this section, if the concentration of the substance is one percent or greater by weight of the mixture, then, for purposes of determining whether a threshold quantity is present at the stationary source, the entire weight of the mixture shall be treated as the regulated substance unless the owner or operator can demonstrate that the mixture itself does not have a National Fire Protection Association flammability hazard rating of 4. The demonstration shall be in accordance with the definition of flammability hazard rating 4 in the NFPA 704, Standard System for the Identification of the Hazards of Materials for Emergency Response, National Fire Protection Association, Quincy, MA, 1996. Boiling point and flash point shall be defined and determined in accordance with NFPA 30, Flammable and Combustible Liquids Code, National Fire Protection Association, Quincy, MA, 1996. The owner or operator shall document the National Fire Protection Association flammability hazard rating.
Here is the same requirement but in an easier format to read (Source)
Flammable mixtures are subject to the rule ONLY if there is a regulated substance in the mixture ABOVE one percent AND the entire mixture meets the NFPA – 4 criteria. If the mixture meets BOTH of these criteria, you must use the weight of the entire mixture (not just the listed substance) to determine if you exceed the threshold quantity. The NFPA-4 definition is as follows:
“Materials that will rapidly or completely vaporize at atmospheric pressure and normal ambient temperature or that are readily dispersed in air, and that will burn
readily. This degree usually includes:
Flammable gases
Flammable cryogenic materials
Any liquid or gaseous material that is liquid while under pressure and has a flash point below 73 F (22.8 C) and a boiling point below 100 F (37.8 C) (i.e., Class 1A flammable liquids)
Materials that will spontaneously ignite when exposed to air.”
So as we can see, if the concentration of the substance is one (1) percent or greater by weight of the mixture, then, for purposes of determining whether a threshold quantity is present in the process, the entire weight of the mixture must be treated as the regulated substance if the NFPA flammability hazard rating is “4”.
From an OSHA perspective, OSHA could care less what the NFPA rating is a mixture! OSHA uses the HAZCOM categorization for flammables…
1910.119(a)(1) This section applies to the following:
1910.119(a)(1)(i) A process which involves a chemical at or above the specified threshold quantities listed in Appendix A to this section;
1910.119(a)(1)(ii) A process which involves a Category 1 flammable gas (as defined in 1910.1200(c)) or a flammable liquid with a flashpoint below 100 °F (37.8 °C) on site in one location, in a quantity of 10,000 pounds (4535.9 kg) or more …
So 1910.119 Appendix A list ONLY the toxic and reactive, as is evident in its title:
1910.119 App A – List of Highly Hazardous Chemicals, Toxics, and Reactives (Mandatory)
OSHA chose NOT to list every flammable by name and CAS #; rather they merely stated the standard applies to ALL Category 1 Flammable Gasses and any flammable liquid that has an FP < 100F.
I realize there have been some recent debates about the NFPA ratings of certain chemicals now that OSHA’s GHS (Hazcom) is in effect and many manufacturers have decided not to include the NFPA ratings on their new SDS(s). But know this, it matters NOT what the NFPA Flammable rating an employer chooses to use on their flammable(s) – it matters how the chemical is categorized using 1910.1200 App B – Physical Criteria (Mandatory). So an employer can determine the best NFPA rating for their chemical within their use and process is best represented by using a “2” in the NFPA flammability; however, this NFPA rating of a “2” means NOTHING in regards to OSHA PSM application when the chemical is a Category 1 Flammable gas or a flammable liquid with a flashpoint below 100 °F, as defined by 1910.1200 App B – Physical Criteria (Mandatory).
I am well aware that NFPA 704 allows for some variation in the ratings an employer uses in that it states:
4.2.3.1 Based on professional judgment, the hazard rating shall be permitted to be either increased or decreased to more accurately assess the likely degree of hazard that will be encountered.
4.2.3.2* It shall be anticipated that different physical forms of the material or conditions of storage and use could result in different ratings being assigned to the same material.
*A.4.2.3.2 Due to the large number of variables, the requirements and guidance presented in this standard are general in nature and are limited to the most important and common factors. For example, although the flash point is the primary criterion for assigning the flammability rating, other criteria could be of equal importance. For example, autoignition temperature, flammability limits, and susceptibility of a container to failure due to fire exposure also should be considered. For instability, the emphasis is on the ease by which an energy-releasing reaction is triggered. These factors should all be considered when calling on one’s judgment during the assignment of ratings.
This seems to be line items that some try to use in their argument when referring to the NFPA rating and OSHA’s PSM application. These items can be used to change your NFPA Flammability ratings, but as I stated above – THIS HAS NO IMPACT ON WHETHER THE FLAMMABLE MATERIAL(s) ARE COVERED OR NOT! What matters is how the flammable is categorized using 1910.1200 App B – Physical Criteria (Mandatory) or better yet, how the SDS classifies the material based on 1910.1200 App B – Physical Criteria (Mandatory).
So the NFPA Flammable rating ONLY applies when dealing with EPA’s RMP rule and has NOTHING to do with the application of OSHA’s PSM standard.