Sprinkler Protection for Flammable and Combustible Liquids

Blog Post created by boconnor Employee on Nov 6, 2020

We live in a world where flammable and combustible liquids are all around us. Gasoline, rubbing alcohol, nail polish remover, hand sanitizer, and cooking oils are just a few common examples. When storing large quantities of flammable liquids, it’s important to understand how to protect them properly because of their rapid rate of fire growth. This blog will dive into some of the requirements for the sprinkler protection of stored flammable and combustible liquids. Designers will often go to NFPA 13 Standard for the Installation of Sprinkler Systems for all sprinkler system requirements, but many don’t know that flammable and combustible liquid storage is covered by NFPA 30 Flammable and Combustible Liquids Code.


What is a flammable or combustible liquid?


Before discussing sprinkler protection requirements for these liquids, the first step is figuring out what exactly we’re talking about when we say flammable or combustible liquids. When defining these liquids, we often refer to their flash point, which is the temperature at which a liquid gives off enough vapor to form an ignitable mixture with the air. With that in mind we define flammable and combustible liquids as follows:

Flammable liquid – flash point below 100°F (37.8°C)

Combustible liquid – flash point at or above 100°F (37.8°C)

NFPA 30 then further divides flammable and combustible liquids into classifications.  These will be used to determine the correct design criteria to your storage. Classifications of flammable and combustible liquids are as follows:

Flammable Class IA = Flash Point <73°F (22.8°C) & Boiling Point < 100°F (37.8°C)

Flammable Class IB = Flash Point < 73°F (22.8°C) & Boiling Point > 100°F (37.8°C)

Flammable Class IC = Flash Point between 73°F (22.8°C) and 100°F (37.8°C)

Combustible Class II = Flash Point between 100°F (37.8°C) and 140°F (60°C)

Combustible Class IIIA = Flash Point between 140°F (60° C) and 200°F (93°C)

Combustible Class IIIB = Flash Point above 200°F (93°C)


Gathering information


When determining when and how to protect the storage of flammable and combustible liquids it is important to gather information to make the correct design decisions. First it is important to know which standards to follow. For the storage of flammable and combustible liquids we should start in NFPA 30. There are certain requirements in NFPA 30 that will instruct users to follow the requirements for various commodities in NFPA 13 when necessary.


To determine design criteria, you will first need to know the quantity of flammable or combustible liquids being stored. As well as how the liquid is being stored (whether it is rack storage, shelf storage palletized, or stacked.)

Next, you need to be aware of what containers the liquid is stored in. The type of containers for flammable and combustible liquids can be stored in varies greatly; some examples of acceptable container material include metal, plastic, or glass. The material the container is made of will also dictate the volume of the container that the liquid can be stored in. A complete list of acceptable containers is located in section 9.4.1 in NFPA 30.


How to protect it


Fire protection system design criteria for protecting the storage of containers of flammable and combustible liquids are provided in Chapter 16 of NFPA 30. The design criteria are contained in 12 tables that address different storage situations and configurations and include both sprinkler and foam-water sprinkler systems. Three decision trees assist the user in identifying the appropriate table to be used. In these tables you will find maximum storage height, maximum ceiling height, required aisle width, required sprinkler arrangement as well as if in-rack sprinklers are required.

It is important to understand that sprinkler systems are designed to protect against certain hazards and increasing those hazards can cause your fire protection system to be overwhelmed. This issue can be addressed by developing a change management plan that triggers safety and compliance reviews when certain changes occur.

Although NFPA 13 usually contains all of the requirements for the installation of sprinkler systems for the storage of flammable and combustible liquids NFPA 13 and NFPA 30 work in harmony to help ensure sprinkler systems are designed in a way that can help save people and property.


Check out the November/December 2020 issue of the NFPA Journal where the ‘In Compliance’ column talks specifically about how to properly store and protect alcohol base hand rub.


Have you recently worked on a project that included flammable or combustible liquids? Let us know in the comments below what you think the biggest or most common challenge is.


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