Flash Point Testing Standards: ASTM D92, D93, ISO 2592/2719, GB/T 3536/261

The two families

Almost every flash point standard belongs to one of two families, defined by the cup type:

Open cup - Cleveland configuration. Vapour escapes, so the measured temperature is higher.

Closed cup - Pensky-Martens (or small-scale) configuration. Vapour is confined, so the measured temperature is lower.

Within each family, regional bodies (ASTM, ISO, IP, GB/T) publish aligned but separately numbered methods.

Open cup standards

ASTM D92 / ISO 2592 / GB/T 3536 / IP 36

The Cleveland open cup. Used for lubricating oils, heavy fuel oils, and other high-flash liquids. GB/T 3536 is the Chinese national method and is the form most often cited by domestic manufacturers and utilities. The method reports the temperature of the flash; Cleveland apparatus can also determine the fire (burning) point.

Closed cup standards

ASTM D93 / ISO 2719 / GB/T 261 / IP 34

The Pensky-Martens closed cup. The reference for petroleum products, diesel, biodiesel, and a wide range of chemicals. GB/T 261-2021 is the current Chinese national method. Because the closed cup value feeds SDS, GHS/CLP, and UN transport classification, it is the more frequently specified method for trade and compliance.

Small-scale closed cup

For very low-flash liquids, paints, and solvents, small-scale methods such as ASTM D3828 / D7236, ISO 3679, and GB/T 5208 (Abel, Tag, Setaflash) are used. They need only a few millilitres of sample.

Side-by-side

Family	ASTM	ISO	GB/T	IP	Primary use
Open cup	D92	2592	3536	36	Lubricating & fuel oils
Closed cup (PM)	D93	2719	261	34	Petroleum, diesel, chemicals
Closed cup (small)	D3828 / D7236	3679	5208	-	Low-flash, paints, solvents

How to choose the right standard

Start from the product specification or regulation. It names the method; that name is binding.

Match the family first, then the region. If the spec says "closed cup (Pensky-Martens)," ASTM D93, ISO 2719, and GB/T 261 are the aligned choices depending on where you ship.

Note the edition year. Methods are revised; cite the version your accreditation or customer requires (e.g. GB/T 261-2021).

Label every result with its method. Never submit an open cup number where a closed cup standard is demanded, or the reverse.

Equipment that covers both families

A lab serving multiple industries typically keeps one open cup and one closed cup instrument:

Open cup: Automatic Cleveland Open Cup Tester, MEBS-6914C (ASTM D92 / GB/T 3536).

Closed cup: Automatic Closed Cup Tester, MOEORW-ES36 (ASTM D93 / GB/T 261-2021).

Still deciding between methods? The Open Cup vs Closed Cup article explains the practical differences with a selection table.

Frequently asked questions

What is the difference between ASTM D92 and ASTM D93?

ASTM D92 is the Cleveland open cup method and is used for lubricating oils, heavy fuel oils, and other high-flash liquids. ASTM D93 is the Pensky-Martens closed cup method and is used for petroleum products, diesel, biodiesel, and many chemicals. The open cup value is generally higher than the closed cup value for the same sample, so the two standards are not interchangeable.

Are ISO and ASTM flash point methods equivalent?

In many cases the methods are technically aligned: ISO 2592 corresponds to the Cleveland open cup (ASTM D92), and ISO 2719 corresponds to the Pensky-Martens closed cup (ASTM D93). GB/T 3536 and GB/T 261 are the Chinese national equivalents of the open and closed cup methods respectively. Always cite the exact standard required by the product specification or regulation.

Can I report a closed cup value where an open cup standard is required?

No. Because open and closed cup results differ, the governing standard defines which method is valid. If a specification calls for ASTM D92 (open cup), a closed cup (ASTM D93) number does not satisfy it, and vice versa. When both are measured, label each clearly.