- capability concerns:
- substitution of personnel 
- training program modifications 
- organizational structure issues:
- changes to job assignments 
- changes to reporting authority 
- external impacts:
- changes in “nonprocess” safeguards (e.g. diminished capabilities from off-site response organizations) 
- significant external events that could impact a process 
Systemic Change Effects
How various changes interact with each other is not explicitly identified in any regulation as an issue which triggers an MOC, since it’s assumed that change interactions are addressed during the hazards analysis. Nonetheless, there are two classes of changes which warrant consideration:
- cumulative impact of multiple changes , also known as “slow drift in conditions”. E.g.
- multiple personnel reductions, which may make emergency response more difficult 
- the effects of incremental changes to safety instrumented system 
- incremental increases in amount of combustables can eventually render existing fire protection inadequate 
- a given change violating the assumptions of a previous change 
New Items versus Changes
An aggressive or legalistic interpretation of the word “change” may conclude that a new item or an additional item isn’t a change, because one cannot change something that doesn’t exist. In today’s vernacular, one can only say, “Good luck with that” since there’s no regulatory support for such a notion. A more rigorous argument would look something like this:
- every new item or addition occurs at a given level in some hierarchy: e.g. adding a relief valve on a line.
- each level in a hierarchy has a higher level: e.g. a line is part of the piping arrangement for the unit
- when an item is added, it’s new or additional at its own level, but it’s a change at the next level up in the hierarchy: e.g. adding a relief valve is a change to the piping arrangement.
But what if an entirely new unit is to be added? Is that still a change? That question was asked shortly after the PSM regulations were promulgated :
How can we determine the point where changes to an existing facility have become so extensive that it should be considered a “new” facility? We find the PSM standard to be very clear in the definition of “replacement in kind” and how to determine the point when a facility is considered “modified’, but less clear on the issue of when changes have progressed beyond “modification”.
OSHA responded that, generally speaking, a new unit on an existing site is a change :
Please note under paragraph 1910.119(b), “Definitions” that a “facility” means buildings, containers and equipment which contain a process. A facility constructed on a work site where there are no other facilities is considered a new facility…A facility, subsequently constructed on the work site such that it is physically separated from and otherwise independent from existing facilities, is considered a new facility. (A facility is considered independent when the facility including the process(es) contained in the facility would not affect or be affected by an existing facility including the process(es) it contains. Otherwise the facility is considered a dependent facility.) …A facility, subsequently constructed on the work site such that the facility or the process(es) it contains is connected to or otherwise dependent on an existing facility including the process(es) it contains, is considered collectively to be a modified facility.
Process Safety Information
The OSHA definition of what constitutes a change is:
(l) Management of change.
The employer shall establish and implement written procedures to manage changes (except for “replacements in kind”) to
- process chemicals,
- equipment, and
- procedures; and,
- changes to facilities that affect a covered process.
The first three items in the list relate to paragraphs (1), (2) and (3) of the “process safety information” definition :
Process safety information. In accordance with the schedule set forth in paragraph (e)(1) of this section, the employer shall complete a compilation of written process safety information before conducting any process hazard analysis required by the standard. The compilation of written process safety information is to enable the employer and the employees involved in operating the process to identify and understand the hazards posed by those processes involving highly hazardous chemicals. This process safety information shall include information pertaining to the hazards of the highly hazardous chemicals used or produced by the process, information pertaining to the technology of the process, and information pertaining to the equipment in the process.
1 Information pertaining to the hazards of the highly hazardous chemicals in the process. This information shall consist of at least the following:
- Toxicity information;
- Permissible exposure limits;
- Physical data;
- Reactivity data:
- Corrosivity data;
- Thermal and chemical stability data; and
- Hazardous effects of inadvertent mixing of different materials that could foreseeably occur. Note: Material Safety Data Sheets meeting the requirements of 29CFR1910.1200(g) may be used to comply with this requirement to the extent they contain the information required by this subparagraph.
(2) Information pertaining to the technology of the process.
- Information concerning the technology of the process shall include at least the following:
- A block flow diagram or simplified process flow diagram (see appendix B to this section);
- Process chemistry;
- Maximum intended inventory;
- Safe upper and lower limits for such items as temperatures, pressures, flows or compositions; and,
- An evaluation of the consequences of deviations, including those affecting the safety and health of employees.
(ii) Where the original technical information no longer exists, such information may be developed in conjunction with the process hazard analysis in sufficient detail to support the analysis.
3) Information pertaining to the equipment in the process.
- Information pertaining to the equipment in the process shall include:
- Materials of construction;
- Piping and instrument diagrams (P&ID’s);
- Electrical classification;
- Relief system design and design basis;
- Ventilation system design;
- Design codes and standards employed;
- Material and energy balances for processes built after May 26, 1992; and,
- Safety systems (e.g. interlocks, detection or suppression systems).
- The employer shall document that equipment complies with recognized and generally accepted good engineering practices.
- For existing equipment designed and constructed in accordance with codes, standards, or practices that are no longer in general use, the employer shall determine and document that the equipment is designed, maintained, inspected, tested, and operating in a safe manner.
The OSHA definition for process safety information, “PSI”, is not comprehensive. Words like “consist of at least”, “include at least” and “shall include” give an indication that the listed items are a minimum, and the expectation is that there may be many more items which belong to process safety information.
The following sections provide a much more comprehensive list of PSI items, based on recognized published references. However, it is impossible for any author to create a complete list, since that would require an understanding of all process safety risks and the names of the documents which permit perpetual safe operation in the presence of those risks. At best, a more comprehensive list can be presented with the intention of providing some benefit to the reader.
Highly Hazardous Chemicals in the Process
The PSM regulation identifies a number of information items that are important for understanding the hazards of highly hazardous chemicals. It further states, “Material Safety Data Sheets meeting the requirements of 29CFR1910.1200(g) may be used to comply with this requirement to the extent they contain the information required by this subparagraph.”
29CFR1910.1200(g)  does not specify any format or organization for Material Safety Data Sheets. But, ANSI Z400.1 does provide a structure for MSDSs. The following list inserts key process safety information items into the ANSI Z400.1 structure.
Information pertaining to the hazards of the highly hazardous chemicals in the process includes:
Section 1 Product and company identification
- name , noting that vendors may use different names or trade names 
- trade name(s) 
- chemical formula
Section 2 Hazards identification
Section 3 Composition/information on ingredients
Section 4 First aid measures
Section 5 Fire fighting measures
Section 6 Accidental release measures
Section 7 Handling and storage
Section 8 Exposure controls/personal protection
- permissible exposure limits 
Section 9 Physical and chemical properties
- physical data1 
- thermodynamic data5
- explosive properties
Section 10 Stability and reactivity
- reactivity data5 
- corrosivity data 
- thermal and chemical stability data 
- hazardous effects of inadvertent mixing 
- reaction kinetics
Section 11 Toxicological information
Section 12 Ecological information
Section 13 Disposal considerations
Section 14 Transport information
Section 15 Regulatory information
Section 16 Other information
Technology of the Process
Information concerning the technology of the process includes:
- block flow diagram or simplified process flow diagram [1, 12]
- process narrative description 
- operating philosophy, operating margin
- s, error-likely situations 
- operating manuals
- safe upper and lower limits on temperature, pressure, flow rates and compositions [1, 4, 12]
- safe upper and lower limits on pH, vibration, rate of reaction, contaminants, availability of utilities 
- consequences of deviation 
- on equipment
- on employees
- unit throughput changes 
- process chemistry 
- raw materials
- feedstocks 
- waste streams and by-products
- reactive chemicals5
- residues 
- maximum intended inventory [1, 12]
- design basis ; see the section on RAGAGEP, below
- special design considerations5
Note that the collection of safe upper and lower limits for all of the process parameters is often termed “operating parameters”. A graphical depiction of safe ranges is often called the “operating envelope”.
Equipment in the Process
Information pertaining to the equipment in the process includes: