T.R. Consulting, Inc.

February 2003 Safety Article

Written and compiled by:

Tony Rieck

Copyright 2003 T.R. Consulting, Inc.




T.R. Consulting, Inc. regularly publishes safety and environmentally related articles on our website at http://www.trconsultinggroup.com/safety/archive.html. These articles are a free service provided by T.R. Consulting, Inc. to all interested parties in order to promote safety and environmental awareness.  T.R. Consulting, Inc. also provides safety training information and services.  Information about our safety training programs can be accessed at http://www.trconsultinggroup.com/safety/.





Employees working on sites that can cause injury or illness need to conduct three basic steps:


* Recognition

* Evaluation

* Control


These steps are not necessarily sequential, but are generally repeated continually at a site as more is learned about the site and as the characteristics of the site change due to activities conducted at the site.


Recognition means knowing what you might be exposed to and how it acts in the environment or interacts wit your body.  For a petroleum service worker, this task is relatively simple when compared to someone approaching a site with hundreds of unlabeled drums.  The basic characteristics and hazards associated with petroleum products are relatively well understood.  On the other hand, it is impossible to assess all of the potential hazards of an unidentified chemical or group of chemicals.  The more that is known about a site and the chemical hazards on the site, the easier the recognition process becomes.


The more that is known about the chemicals involved, the easier the initial hazard recognition process becomes.


Some information that might be useful includes:





The above information can help to build a body of information that can be used to recognize the potential problems posed by the release of a material into the environment. 


The material safety data sheet (MSDS) published by the manufacturer or the NIOSH/OSHA “Pocket Guide to Chemical Hazards” are good reference tools for aid in determining the level of risk and the routes of exposure associated with a chemical.


Once this information is known, it is time to evaluate real and potential effects.  Evaluation is a process of assessing real versus potential hazard.  In other words, evaluation is the process of determining the level of risk associated with exposures at a site.  A tanker car damaged in an accident is only a potential hazard if the tank did not rupture.  The hazard to the public from a gas line rupture at a remote site is far less than from a rupture in close proximity to a school.  The presence of gasoline vapors in an excavation where gasoline tanks have been removed from the ground may be shown through monitoring to pose a flammability hazard or to exist at such low levels that site personnel will not be adversely exposed.  Again, the worker is presented with a need to understand the chemical’s properties in order to properly evaluate the potential for harm.


Some information that could be useful evaluating the risk associated with exposure to a chemical (in addition to the information discussed above) includes:



Once the identity of the chemical is known, the risks associated with it identified and the site has been evaluated, it is easier to prescribe appropriate controls to prevent overexposure of site personnel, protect the public and to minimize environmental impacts.  Controls include engineering controls such as ventilation, wetting of dusts, protective clothing and respiratory equipment.  It is preferable to eliminate potential exposures to site personnel and the public.  When engineering controls are insufficient to provide for the safety of site personnel, personal protective equipment is assigned which will reduce employee exposures below published safe exposure limits.





Using the information provided about a chemical requires an understanding of the terms used to describe the chemical.  Several of the more common terms used to describe a chemical’s physical properties and exposure limits are listed below:



Other important physical properties may also be available. 


-         Vapor pressure is the characteristic pressure exerted by a vapor in equilibrium with its liquid or solid form against the atmosphere.  The vapor pressure increases with temperature.  It is essential to understand the effects of vapor pressure when using a pump to “lift” a liquid in order to avoid cavitation of the pump.

-         Viscosity is the resistance to flow exhibited by a liquid.

-         Ionization Potential (IP) is the amount of energy that must be applied to a chemical to remove the outermost electron and impart a measurable charge.  The NIOSH Pocket Guide is the only readily available source with this information that is necessary for the proper operation of Photo Ionization Detector (PID) or the Flame Ionization Detector (FID).

-         Molecular Weight is the sum of the atomic weights of the atoms in a molecule.


Both the MSDS and the NIOSH Pocket Guide provide information on target organs, symptoms of exposure and first aid measures to be implemented when exposure occurs.  The NIOSH Pocket Guide contains numerous abbreviations that are explained in supplementary sections of the book.  Importantly, the NIOSH Pocket Guide provides information on appropriate selection of respirators and indications when other safety devices or measures are required (such as quick drench or periodic change of protective clothing).  For more complex chemicals, the MSDS provides breakdowns on the exposure potential for each of the components.  A proper approach to proper assessment is to incorporate both the MSDS and the NIOSH Pocket Guide into routine use.


Special note regarding PEL information:  In July 1992, the 11th Circuit Court of Appeals in its decision in AFL-CIO v. OSHA, 965 F.2d 962 (11th Cir., 1992) vacated more protective PELs set by OSHA in 1989 for 212 substances, moving them back to PELs established in 1971 (these values were extracted from the 1968 ACGIH TLV Booklet). The appeals court also vacated new PELs for 164 substances that were not previously regulated. The substances for which OSHA PELs were vacated on June 30, 1993 are indicated by the symbol "†" following OSHA PEL in this column.  For chemicals that were affected by this lawsuit, special consideration should be given to decisions affecting employee exposures in the field as the stated PEL may be under protective.