Glossary of Terms: S

Safe Area
Work area in which there is no danger of contamination with explosive gases.
Sampling
The process of taking small representative quantities of a gas, liquid, or solid for the purpose of analysis.
SARA
Superfund Amendments and Reauthorization Act of 1986. (US Environmental Protection Agency)
SCBA
Self-contained breathing apparatus.
Semiconductor sensor
Type of sensor that uses semiconductor material in construction.
Sensitizer
A substance which on first exposure causes little or no reaction but which on repeated exposure may cause a marked response not necessarily limited to the contact site. Skin sensitization is the most common form of sensitization in the industrial setting. Respiratory sensitization to a few chemicals (for example, isocyanates) is also known to occur.
Short-term exposure limit (STEL)
ACGIH-recommended exposure limit. Maximum concentration to which workers can be exposed for a short period of time (15 minutes) for only four times throughout the day with at least one hour between exposures.
SIL
Safety Integrity Levels
Single channel
One point of detection or input
Skin
A notation sometimes used with Threshold Limit Value (TLV) or Time-Weighted
SLM
Sound level meter
Smart
Used to describe a sensor with on-board memory that stores sensor information such as calibration details, date of manufacture, gas type etc.
Solubility in water
A term expressing the percentage of a material (by weight) that will dissolve in water at ambient temperature. Solubility information can be useful in determining spill cleanup methods and re-extinguishing agents and methods for a material.
Solvent
A substance, usually a liquid, in which other substances are dissolved. The most common solvent is water. Many solvents are flammable.
Sorbent
(1) A material that a removes toxic gases and vapors from air inhaled through a canister or cartridge. (2) Material used to collect gases and vapors during air-sampling.
Sound exposure level (SEL)
Averages the sampled sound over a one second period. Assuming the sampled run time to be greater than one second, SEL is the equivalent one-second noise that would be equal in energy to the noise that was sampled. SEL is typically measured using a 3dB exchange rate without a threshold. SEL is not used by OSHA.
Sound level meter
A handheld instrument typically used for measuring environmental decibel levels. For community and environmental noise assessment, maintenance inspections and troubleshooting, and noise ordinance enforcement.
Span
The level at which calibration is made (typically 50% of full scale).
Specific gravity
The ratio of the mass of a unit volume of a substance to the mass of the same volume of a standard substance at a standard temperature. Water at 4oC (39.2oF) is the standard usually referred to for liquids; for gases, dry air (at the same temperature and pressure as the gas) is often taken as the standard substance. See Density.
SPL
Sound pressure level
Stability
An expression of the ability of a material to remain unchanged. For MSDS purposes, a material is stable if it remains in the same form under expected and reasonable conditions of storage or use. Conditions which may cause instability (dangerous change) are stated. Examples are temperatures above 150oF, shock from dropping.
Stable
The tendency of a material to remain in the same form under reasonable conditions of storage or use. Compare with unstable.
Static electricity
An electrical charge that cannot move. This charge will eventually develop enough energy to jump as a spark to a nearby grounded or less highly charged object. If sparks occur in an ignitable vapor or dust mixture, it can cause an explosion or fire.
Static pressure
The pressure in a duct that tends to burst or collapse the duct; may be positive or negative, usually measured in in inches of WC
STEL
Short Term Exposure Limit, usually monitored over 15 minute periods.
Stress
A set of physical reactions that take place in the body in response to demands that are placed on it. These reactions prepare the body for action.
Substitution
The replacement of toxic or hazardous materials, equipment or processes with those that are less harmful.
Synergism
Cooperative action of substances whose total effect is greater than the sum of their separate effects.
Synergistic effects
The health effects of two or more substances or agents that are greater than the sum of their separate effects.
Synonym
Another name or names by which a material is known. For example, methyl alcohol is also known as methanol or wood alcohol.
Systemic
Spread throughout the body, affecting all body systems and organs, not localized in one spot or area.