| The Home page of ILPI's Safety Data Sheet (SDS) Resource, the leader in SDS information since 1995! | |
| The history and philosophy behind this resource. | |
| A curated collection of books and reference materials concerning Safety Data Sheets and closely related topics. | |
| Paste your plain text SDS into the SDS-Demystifier, and it will be converted into a hypertext-enriched document with links to detailed explanations of each key term. | |
| An extensive list of frequently asked questions about Safety Data Sheets including regulations, content, compliance, and more. | |
| A humorous take on Safety Data Sheet jargon. Fill in the blanks on our entry form to generate a personalized Unsafety Data Sheet to share with your coworkers. | |
| Since 1995, we've maintained this massive curated list of the best places to find Safety Data Sheets on the Internet. | |
| You are here! Way more than a glossary, this hypertext-enhanced resource covers hundreds of SDS-related terms and expert knowledge. Each entry includes both the SDS relevance and links to additional authoritative resources. | |
| Archived results of Safety Data Sheet related polls taken by some of our millions of site visitors | |
| The OSHA regulations behind SDS regulations, including the inspection guidelines and over 400 official interpretations letters under the Hazard Communication Standard | |
| Commercial suppliers of SDS authoring and management software as well as cloud compliance services. | |
| Commercial companies that will create SDS's for your specific needs as well as SDS translation companies. |
Safety signs, banners, and scoreboards? Get yours at Safety Emporium!
Pressure Unit Conversions
Definition
Pressure is a measure of the force against a surface. Pressure is usually expressed as a force per unit area.
Here is a handy conversion calculator for some common pressure terms. The definitions of each term are in the following section.
Additional Info
Many of the items you will find on a Safety Data Sheet come in both English (U.S. Customary System) and metric (International System or SI or cgs) units. The metric system has been adopted by almost every country except the United States. Even in the U.S., scientists and technical people use the metric system because of its ease of use.
If you are unfamiliar with the terms used in these definitions, see our mass unit and distance unit conversion pages.
| Unit | Equivalent measurements, comments | |
|---|---|---|
| Pounds per square inch (psi, PSI, lb/in2, lb/sq in) | Commonly used in the U.S., but not elsewhere. Normal atmospheric pressure is 14.7 psi, which means that a column of air one square inch in area rising from the Earth's atmosphere to space weighs 14.7 pounds. | |
| Atmosphere (atm) | Normal atmospheric pressure is defined as 1 atmosphere. 1 atm = 14.6956 psi = 760 torr. | |
| Torr (torr) | Based on the original Torricelli barometer design, one atmosphere of pressure will force the column of mercury (Hg) in a mercury barometer to a height of 760 millimeters. A pressure that causes the Hg column to rise 1 millimeter is called a torr (you may still see the term 1 mm Hg used; this has been replaced by the torr. "mm Hg" is commonly used for blood pressure measurements). 1 atm = 760 torr = 14.7 psi. | |
| Bar (bar) | The bar nearly identical to the atmosphere unit. One bar = 750.062 torr = 0.9869 atm = 100,000 Pa. | |
| Millibar (mb or mbar) | There are 1,000 millibar in one bar. This unit is used by meteorologists who find it easier to refer to atmospheric pressures without using decimals. One millibar = 0.001 bar = 0.750 torr = 100 Pa. | |
| Pascal (Pa) | 1 pascal = a force of 1 Newton per square meter (1 Newton = the force required to accelerate 1 kilogram one meter per second per second = 1 kg.m/s2; this is actually quite logical for physicists and engineers, honest). 1 pascal = 10 dyne/cm2 = 0.01 mbar. 1 atm = 101,325 Pascals = 760 mm Hg = 760 torr = 14.7 psi. | |
| Kilopascal (kPa) | The prefix "kilo" means "1,000", so one kilopascal = 1,000 Pa. Therefore, 101.325 kPa = 1 atm = 760 torr and 100 kPa = 1 bar = 750 torr. | |
| Megapascal (MPa) | The prefix "mega" means "1,000,000", so one megapascal = 1,000 kPa = 1,000,000 Pa = 9.869 atm = 145 psi. | |
| Gigapascal (GPa) | The prefix "giga" means "1,000,000,000", so one gigapascal = 1,000 MPa = 1,000,000 kPa = 1,000,000,000 Pa = 9,870 atm = 10,000 bar. Pressures of several gigapascals can convert graphite to diamond or make hydrogen a metallic conductor! Such high pressures are rarely encountered in everyday life. |
Some Worked Examples
CORRECT: Convert 5 atm to psi:
WRONG: Convert 5 atm to psi:
CORRECT: Convert 4,000 pascal to torr:
Safety Emporium has gas cylinder signs, racks, carts, clamps, lockouts and more to ensure your workers' safety.
SDS Relevance
Be very careful to note the units when reading numbers on a Safety Data Sheet. If you ever perform a calculation of any sort, always remember to write the units next to each number in your calculation and make sure that they cancel properly. If they don't, your calculation was incorrect!
Further Reading
- Metric Information and Conversions Home Page at the National Institute of Standards.
- More info about the metric system, including prefixes, at ChemTeam.
- The U.S. Metric Association (USMA) has all sorts of useful information and history on the metric system.
- Pressure explosions can have terrifying results. See this utterly remarkable account of a large liquid nitrogen Dewar explosion at UC Davis courtesy of the internet way back machine (9 MB, PDF) as an example.
See also: area units, distance units, mass units, energy units, mole, temperature units, vapor pressure, volume units.