What is a flashpoint?

A flash point is defined as the lowest temperature at which the vapors of a volatile material can ignite. Meaning, that if a liquid is exposed to an external heat source, such as a spark or flame- the vapor released is capable of forming an ignitable vapor or air mixture. 

To further help you gain a better understanding of what is a flash point, let's take a standard definition of flash point from the International Electrotechnical Commission:

A flash point is the lowest temperature at which the vapors of a volatile material can ignite. This is an important factor when evaluating safety precautions in any area where flammable materials are used. In many factories, great care must be taken to ensure the temperature never approaches the flash point of various materials or it could cause serious dangers.

Difference Between Flash Point And Fire Point 

Fire Point vs Flash Point

Unlike the flash point, the fire point is the lowest temperature at which the vapors of an ignitable or volatile liquid keep burning long after the ignition or heat source has been removed. In the occurrence of a flash point, the vapors are not reactive enough to sustain burning for a defined period. 

However, the stark difference between the flash and fire point is that they both start at the “lowest temperature”, the fire point is higher in terms of temperature in comparison to the flash point. 

Flash Point vs Ignition Temperature:

Occasionally the flash point is sometimes confused with the autoignition temperature, which is categorized as the lowest temperature at which the chemical substance will spontaneously combust without the help of an ignition source. 

Unlike the ignition temperature, a flash point requires an ignition source. The flash point is the normal lowest temperature at which the vapors will spark or ignite if they meet an external ignition or heat source. 

With the help of an example, let’s further evaluate the difference between flash point and ignition temperature: If one were to take vegetable oil and put it in an area that was 621 degrees (its flash point) it would not actually ignite unless there were an ignition point (a flame or spark, for example). Despite this fact, however, one must always take great care whenever working with hazardous materials in temperatures anywhere near their flash point or autoignition temperature. This further explains that unlike ignition temperature, at which chemicals or substances automatically combust, for a flash point to occur an external source like heat is required. 

How To Measure Flash Point 

When working to determine the flash point of a material two measurements can be used:

1. Open Cup Flash Point Measurement

To measure a flash point using the open-cup method, you’ll need:

The vessel should be exposed to outside air and not in a controlled environment such as a lab or indoors. Once the sample is placed inside the container, you will bring the heat source such as flame or spark at various temperatures and continue to do so until it ignites. That temperature at which the substance ignited will be categorized as the flash point. 

2. Closed Cup Flash Point Measurement 

There are actually two types of closed cup measurements. The first is where the vapors above a liquid and the vapors are not of equal temperature and the other is where they are. In either case, the cups are sealed with a lid that has a way for a flame to be introduced. As with the open cup measurement, the temperature at which there is ignition is the flash point. Unlike the open cup measurement, the closed cup experiment will be conducted in a closed, controlled environment. Meaning that no interference from the outside will be involved in the measurement process. 

Flash Point of Common Items

Knowing the flash point of various items can help when planning out workplace safety. The following are some of the more common types of fuel or other materials where the flash point is important. All degrees are listed in Fahrenheit: 

Why Measuring Flash Point Is Important? 

1. Quality Assurance:

Petroleum and chemical industries use the flash point measurement method to check if the substance is authentic and if there’s no adulteration or contamination in the product. The fuel and chemicals are transported through common storage tanks which may use common pipelines. Due to this, there is a risk of contamination from external sources which can alter the concentration of the product. 

A flash point measurement method is used to determine whether a contamination of a product has occurred. If the flash point varies from its normal temperature, this will conclude the sample has been contaminated or altered. This is highly important as changes in fuel oil, lubrication oil, and hydraulic oil can lead to mechanical issues in the equipment used in ships, power plants, or other manufacturing machinery. Using the flash point average for fuel and diesel assists companies in maintaining the quality of the products they supply. 

2. Hazard Classification: 

Chemical companies or pharmaceutical labs use the flash point measurement method to identify flammable and combustible materials to classify their hazard potential. Knowing the flash point of volatile substances helps to maintain safety regulations to prevent accidents. 

3. Waste Disposal Regulations: 

Hazard waste regulations can be implemented by identifying the flash point of a flammable substance, so it can be disposed of safely without setting off a chain reaction. 

FAQ’s 

What is a flash point’s main measurement used when considering the ignitability of liquids?

The flash point the the lowest or minimum temperature at which the vapors above the liquid surface will produce an ignitable mixture. Any liquid with a flash point less than 100F falls under the category of a flammable liquid. Any liquid with a flash point between 100F and 200F is combustible. 

What is a flash point of a flammable liquid? 

According to OSHA, the flash point of a flammable liquid is below 100 degrees F (37.8 degrees C). Unless any additional mixtures or components are present, then the flash point will vary depending on the mixture present. 

What is the minimum temperature at which a liquid produces an ignitable vapor? 

The flash point is the minimum temperature at which the liquid forms an ignitable vapor above it’s surface. The temperature at which the liquid begins to do so is categorized as the flash point of that substance. Flammable liquids have a flash point of less than 100°F so, they are easier to ignite. However combustible liquids have a flash point of 100 or 200°F or above. 

What is a flash point in chemistry? 

The minimum temperature at which a liquid begins to vaporize or give off vapors within a vessel to eliminate a spark or short burst of heat with the mixture in the surrounding air is known as the flash point. The lower the flash point the easier it is to ignite a liquid substance, as they will readily spark with a small intensity of heat.