Attachment C 

Inherently Safer Systems Checklist 

Date: June 15, 2011 

C-1 

ATTACHMENT C 

INHERENTLY SAFER SYSTEMS CHECKLIST

The intent of this checklist is to stimulate discussion and thinking about process improvements, 

and to encourage the concept of avoiding and reducing hazards, not just preventing/ mitigating 

consequences of hazard by adding protective equipment. “Out-of-the-box” thinking is strongly 

encouraged. The content of this checklist was extracted from CCPS “Inherently Safer Chemical 

Processes: A Life Cycle Approach”1

 (ISCP Book). 

The checklist questions are not always pertinent for an individual facility or for every phase of a 

new process/project or an existing facility. The checklist should be tailored for your facility and 

for the stage the checklist is being applied for new processes, as follows: 

• During the chemistry-forming (synthesis) phase for product/process research and 

development to focus on the chemistry and process 

• During the facilities design scoping and development prior to completion of the 

design basis to focus on equipment and configuration 

• During the basic design phase of the project 

The checklist should also be tailored for existing processes in your facility to be used during a 

Process Hazard Analysis, when appropriate for the Process Hazard Analysis Team. Some items 

may need to be reviewed by a team that is outside of the Process Hazard Analysis Team, because 

the personnel with the appropriate expertise or ability may not be a part of the Process Hazard 

Analysis Team. Issues, such as considering the transportation of hazardous materials, may 

require the ability to renegotiate contracts with shippers. 

CCHMP will review how the Stationary Source determined the appropriate checklist for that 

facility and for the stage of assessment, when the facility is audited or during an unannounced 

inspection. 

CCHMP extracted the worksheet format as presented in the second edition of the ISCP Book as 

approaches to inherently safer systems strategies and incorporated additional considerations and 

provided the following checklist as example questions to consider: 
Attachment C 

Inherently Safer Systems Checklist 

Date: June 15, 2011 

C-2 

No. 

Inherently Safer 

Design Alternative 

Applicable 

Y/N? 

Opportunities

/ Applications Feasibility

Current 

Status Recommendation 

1.0 MINIMIZE 

1.1 Inventory Reduction 

Can hazardous raw 

materials inventory be 

reduced? 

 *Just in time 

deliveries based on 

production needs 

 *Supplier 

management including 

strategic alliance 

 *On-site generation 

of hazardous material 

(including in situ) from 

less hazardous raw 

materials 

1.1.1

 *Hazardous raw 

material inventory 

management system 

based on production 

forecast 

Can (hazardous) inprocess storage and 

inventory be reduced? 

 *Direct coupling of 

process elements 

 *Eliminating or 

reducing size of inprocess storage 

1.1.2

 *Designing process 

equipment involving 

hazardous material 

with the smallest 

feasible inventory (see 

also Section 2.2) 
Attachment C 

Inherently Safer Systems Checklist 

Date: June 15, 2011 

C-3 

No. 

Inherently Safer 

Design Alternative 

Applicable 

Y/N? 

Opportunities

/ Applications Feasibility

Current 

Status Recommendation 

Can hazardous finished 

product inventory be 

reduced? 

 *Improving 

production 

scheduling/sales 

forecasting 

 *Improving 

communication with 

transporters/material 

handlers 

1.1.3

 *Hazardous finished 

product inventory 

management system 

based on sales forecast 

1.2 Process Intensification 

Considerations 

Can alternate 

equipment with 

reduced hazardous 

material inventory 

requirement be used? 

 *Centrifugal 

extractors in place of 

extraction columns 

 *Flash dryers in place 

of tray dryers 

 *Continuous reactors 

in place of batch 

 *Plug flow or loop 

reactors in place of 

continuous stirred tank 

reactors 

 *Continuous in-line 

mixers (e.g., static 

mixer) in place of 

mixing vessels or 

reactors 

1.2.1

 *Intensive mixers to 

minimize size of mixing 

vessel of reactor 
Attachment C 

Inherently Safer Systems Checklist 

Date: June 15, 2011 

C-4 

No. 

Inherently Safer 

Design Alternative 

Applicable 

Y/N? 

Opportunities

/ Applications Feasibility

Current 

Status Recommendation 

 *High heat-transfer 

reactors (e.g., micro 

reactor, HEX reactor) 

 *Spinning-disk reactor 

(especially for high 

heat-flux or viscous 

liquids) 

 *Compact heat 

exchangers (higher 

heat transfer area per 

unit volume, e.g., 

spiral, plate & frame, 

plate-fin) in place of 

shell-and-tube) 

 *More hazardous 

material on the tube 

side in shell-and-tube 

exchangers 

 *Use water or other 

non flammable heat 

transfer medium, a 

vapor-phase medium, 

or a medium below its 

boiling point 

 *Wiped film stills in 

place of continuous 

still pots (distillation 

columns) 

 *Combine unit 

operations (such as 

reactive distillation or 

extraction in place of 

separate reactor with 

multi-column 

fractionation train or 

extractor; installing 

internal reboilers or 

heat exchangers) to 

reduce overall system 

volume 
Attachment C 

Inherently Safer Systems Checklist 

Date: June 15, 2011 

C-5 

No. 

Inherently Safer 

Design Alternative 

Applicable 

Y/N? 

Opportunities

/ Applications Feasibility

Current 

Status Recommendation 

 *Use of acceleration 

fields (e.g., rotating 

packed bed for 

gas/liquid or 

liquid/liquid contacting 

for absorption, 

stripping, distillation, 

extraction, etc.) 

 *Use solid catalyst in 

place of a more 

hazardous liquid 

catalyst 

 *Alternate energy 

sources (such as lasers, 

UV light, microwaves, 

or ultrasound) to 

control reaction or 

direct heat to the unit 

operation 

1.2.2 Has the length of 

hazardous material 

piping runs been 

minimized? 

1.2.3 Has hazardous material 

piping been designed 

for minimum pipe 

diameter? 

1.2.4 Can pipeline inventory 

be reduced by using 

the hazardous material 

as a gas rather than a 

liquid? 

1.2.5 Can process conditions 

be changed to reduce 

production of 

hazardous waste or byproducts? 
Attachment C 

Inherently Safer Systems Checklist 

Date: June 15, 2011 

C-6 

No. 

Inherently Safer 

Design Alternative 

Applicable 

Y/N? 

Opportunities

/ Applications Feasibility

Current 

Status Recommendation 

1.3 Are there any other 

alternatives for 

minimizing the 

inventory of hazardous 

materials in this 

process? 

2.0 SUBSTITUTE 

2.1 Is this (hazardous) 

process/product 

necessary? 

2.2 Is it possible to 

completely eliminate 

hazardous raw 

materials, process 

intermediates, or byproducts by using an 

alternative process or 

chemistry? 

2.3 Is it possible to 

completely eliminate 

in-process solvents and 

flammable heat 

transfer media by 

changing chemistry or 

processing conditions? 

2.4 Is an alternative 

process available for 

this product that 

eliminates or 

substantially reduces 

the need for hazardous 

raw materials or 

production of 

hazardous 

intermediates? 
Attachment C 

Inherently Safer Systems Checklist 

Date: June 15, 2011 

C-7 

No. 

Inherently Safer 

Design Alternative 

Applicable 

Y/N? 

Opportunities

/ Applications Feasibility

Current 

Status Recommendation 

Is it possible to 

substitute less 

hazardous raw 

materials? 

 *Noncombustibles for 

flammable 

 *Less volatile 

 *Less reactive 

 *More stable 

 *Less toxic 

2.5 

 *Low pressure steam 

rather than flammable 

heat transfer fluid (i.e. 

operated above flash 

point) 

2.6 Is it possible to 

substitute less 

hazardous final 

product solvents? 

2.7 Is it possible to use a 

nonflammable 

refrigerant instead of a 

flammable one (or 

minimize inventory)? 

2.8 Are there any other 

alternatives for 

substituting or 

eliminating the use of 

hazardous materials in 

this process? 

3.0 MODERATE 

3.1 Is it possible to limit 

the supply pressure of 

(hazardous) raw 

materials to less than 

the maximum 

allowable working 

pressure of the vessels 

to which they are 

delivered? 
Attachment C 

Inherently Safer Systems Checklist 

Date: June 15, 2011 

C-8 

No. 

Inherently Safer 

Design Alternative 

Applicable 

Y/N? 

Opportunities

/ Applications Feasibility

Current 

Status Recommendation 

3.2 Is it possible to make 

reaction conditions (for 

hazardous reactants or 

products) 

(temperature, 

pressure) less severe 

by using a catalyst, or a 

better catalyst (e.g., 

structured or 

monolithic vs. packedbed)? 

Can the process be 

operated at less severe 

conditions (for 

hazardous reactants or 

products) by 

considering: 

 * Improved kinetics 

or thermodynamics to 

reduce operating 

temperatures or 

pressures 

 * Changes in reaction 

phase (e.g., liquid/ 

liquid, gas/liquid, or 

gas/gas) 

 *Raw material recycle 

to compensate for 

reduced yield or 

conversion 

3.3 

 *Operating at a lower 

temperature to 

prevent runaway 

reactions or material 

failure 
Attachment C 

Inherently Safer Systems Checklist 

Date: June 15, 2011 

C-9 

No. 

Inherently Safer 

Design Alternative 

Applicable 

Y/N? 

Opportunities

/ Applications Feasibility

Current 

Status Recommendation 

Is it possible to use less 

concentrated 

hazardous raw 

materials to reduce the 

hazard potential? 

 *Aqueous ammonia 

and/or HCL instead of 

anhydrous 

 

 *Sulfuric acid instead 

of oleum 

 

 *Dilute nitric acid 

instead of 

concentrated fuming 

nitric acid 

3.4 

 *Wet benzoyl 

peroxide instead of dry 

Is it possible to use 

larger particle 

size/reduced dust 

forming solids to 

minimize potential for 

dust explosions? 

3.5 

 

 *Use particles 

configuration with 

higher Minimum 

Ignition Energy (MIE) 

or surface treat 

particles to change 

conductivity and 

resistivity properties 

that reduce the chance 

of a static charge 

buildup 
Attachment C 

Inherently Safer Systems Checklist 

Date: June 15, 2011 

C-10 

No. 

Inherently Safer 

Design Alternative 

Applicable 

Y/N? 

Opportunities

/ Applications Feasibility

Current 

Status Recommendation 

3.6 Are all process 

materials (e.g., 

heating/cooling media) 

compatible with 

process materials in 

event of inadvertent 

contamination (e.g., 

due to a tank coil or 

heat exchanger tube 

failure)? 

3.7 Is it possible to add an 

ingredient to volatile 

hazardous materials 

that will reduce its 

vapor pressure? 

3.8 For equipment 

containing materials 

that become unstable 

at elevated 

temperature or freeze 

at low temperature, is 

it possible to use 

heating/cooling media 

which limit the 

maximum and 

minimum 

temperatures 

attainable (i.e., selflimiting electric heat 

tracing or hot water at 

atmospheric pressure)? 

3.9 Can process conditions 

be changed to avoid 

handling flammable 

liquids above their 

flash points? 
Attachment C 

Inherently Safer Systems Checklist 

Date: June 15, 2011 

C-11 

No. 

Inherently Safer 

Design Alternative 

Applicable 

Y/N? 

Opportunities

/ Applications Feasibility

Current 

Status Recommendation 

3.10 Is equipment designed 

to totally contain the 

materials that might be 

present inside at 

ambient temperature 

or the maximum 

attainable process 

temperature (i.e., 

higher maximum 

allowable working 

temperature to 

accommodate loss of 

cooling, simplified 

reliance on external 

system like 

refrigeration to control 

temperature such that 

vapor pressure is less 

than equipment design 

pressure)? 

3.11 For processes handling 

flammable materials, is 

it possible to design 

the layout to minimize 

the number and size of 

confined areas and to 

limit the potential for 

serious overpressure in 

the event of a loss of 

containment and 

subsequent ignition? 

Can process units (for 

hazardous materials) 

be designed to limit 

the magnitude of 

process deviations? 

3.12 

 *Selecting pumps 

with maximum 

capacity lower than 

safe rate of addition 

for the process 
Attachment C 

Inherently Safer Systems Checklist 

Date: June 15, 2011 

C-12 

No. 

Inherently Safer 

Design Alternative 

Applicable 

Y/N? 

Opportunities

/ Applications Feasibility

Current 

Status Recommendation 

 *For gravity-fed 

systems, limiting 

maximum feed rate to 

be within safe limits by 

pipe size or fixed 

orifice 

 *Minimum flow 

recirculation line for 

pumps/compressors 

(with orifice to control 

flow) to ensure 

minimum flow in event 

of deadheading or 

surging 

3.13 Can hazardous material 

liquid spills be 

prevented from 

entering drainage 

system/sewer (if 

potential for fire or 

hazardous reaction 

exists, e.g., water 

reactive material)? 

3.14 For flammable 

materials, can spills be 

directed away from the 

storage vessel to 

reduce the risk of a 

boiling liquid 

expanding vapor 

explosion (BLEVE) in 

the event of a fire? 

Can passive designs, 

such as the following, 

be implemented? 

 *Secondary 

containment (e.g., 

dikes, curbing, 

buildings, enclosures) 

3.15 

 *Use of properly 

vented blowdown tank 

for dumping of 

runaway reaction mass 
Attachment C 

Inherently Safer Systems Checklist 

Date: June 15, 2011 

C-13 

No. 

Inherently Safer 

Design Alternative 

Applicable 

Y/N? 

Opportunities

/ Applications Feasibility

Current 

Status Recommendation 

 *Permanent bonding 

and grounding systems 

for process equipment, 

tanks, and vessels 

 *Use of gas inerting 

systems for handling 

flammables and 

explosive dusts (e.g., 

nitrogen, CO2) 

 *Use of dip legs with 

anti-siphon openings 

for feed to flammable 

liquid storage tanks 

 *Fireproofing 

insulation vs. 

fixed/portable fire 

protection 

3.16 Can gases be 

transported and stored 

at low or atmospheric 

pressure on a high 

capacity adsorbent 

instead of using 

pressurized gas 

cylinders? 

3.17 Are there any other 

alternatives for 

moderating the use of 

hazardous materials in 

this process? 

4.0 SIMPLIFY 

Can equipment be 

designed such that it is 

difficult or impossible 

to create a potential 

hazardous situation 

due to an operating or 

maintenance error? 

4.1 

 *Easy access and 

operability of valves to 

prevent inadvertent 

errors 
Attachment C 

Inherently Safer Systems Checklist 

Date: June 15, 2011 

C-14 

No. 

Inherently Safer 

Design Alternative 

Applicable 

Y/N? 

Opportunities

/ Applications Feasibility

Current 

Status Recommendation 

 *Elimination of all 

unnecessary crossconnections 

 *Use of dedicated 

hoses and compatible 

couplings for reactants 

where hose 

connections are used 

 *Designing 

temperature-limited 

heat transfer 

equipment to prevent 

exceeding maximum 

process or equipment 

design temperatures 

 *Use of corrosion 

resistant materials for 

process equipment, 

piping and components 

 *Operating at a higher 

temperature to avoid 

cryogenic effects such 

as embrittlement 

failures 

 *Using alternative 

agitation methods 

(e.g., external 

circulation using 

sealless pump which 

eliminates potential 

releases due to 

agitator seal failures) 

 *Use of mixing feed 

nozzle instead of 

agitator for vessel 

mixing 

 *Using underground 

or shielded tanks 

 *Specifying fail-safe 

operation on utility 

failure (e.g., air , 

power) 
Attachment C 

Inherently Safer Systems Checklist 

Date: June 15, 2011 

C-15 

No. 

Inherently Safer 

Design Alternative 

Applicable 

Y/N? 

Opportunities

/ Applications Feasibility

Current 

Status Recommendation 

 *Allocating redundant 

inputs and outputs to 

separate modules of 

the programmable 

electronic system to 

minimize common 

cause failures 

 *Provide continuous 

pilots (independent, 

reliable source) for 

burner management 

systems 

 *Using refrigerated 

storage vs. pressurized 

storage 

 *Using independent 

power buses for 

redundant equipment 

to minimize 

consequences of 

partial power failures 

 *Minimizing 

equipment wall area to 

minimize corrosion/fire 

exposure 

 *Minimizing 

connections, paths and 

number of flanges in 

hazardous processes 

 *Avoiding use of 

threaded connections 

in hazardous service 

 *Using double walled 

pipe 

 *Minimizing number 

of bends in piping 

(potential erosion 

points) 

 *Using expansion 

loops in piping rather 

than bellows for 

thermal expansion 
Attachment C 

Inherently Safer Systems Checklist 

Date: June 15, 2011 

C-16 

No. 

Inherently Safer 

Design Alternative 

Applicable 

Y/N? 

Opportunities

/ Applications Feasibility

Current 

Status Recommendation 

 *Using expansion 

loops in piping rather 

than bellows for 

thermal expansion 

 *Designing equipment 

isolation mechanisms 

for maintenance in the 

process 

 *Limiting manual 

operations such as 

filter cleaning, manual 

sampling, hose 

handling for 

loading/unloading 

operations, etc. 

 *Designing vessels for 

full vacuum to 

eliminate risk of vessel 

collapse 

 *Designing both shelland-tube side of heat 

exchangers to contain 

the maximum 

attainable pressure, 

eliminating the need 

for pressure relief (may 

still be needed to meet 

fire safety 

requirements) 

 *Designing/selecting 

equipment which 

makes incorrect 

assembly impossible 

 *Using equipment 

that clearly identifies 

status: 

 *Check valves with 

easy to identify 

direction of flow 
Attachment C 

Inherently Safer Systems Checklist 

Date: June 15, 2011 

C-17 

No. 

Inherently Safer 

Design Alternative 

Applicable 

Y/N? 

Opportunities

/ Applications Feasibility

Current 

Status Recommendation 

 *Gate valves with 

rising spindles to 

clearly indicate open or 

closed position 

 *Spectacle (or figure8) blinds instead of slip 

plates 

 *Manual quarter-turn 

block valves with 

handles that clearly 

indicate position 

 *For automated block 

valves, display actual 

valve position in 

addition to the output 

to the valve 

 *Designing equipment 

with an MAWP to 

contain the maximum 

pressure generated 

without reliance on 

pressure relief systems 

even if the "worst 

credible event" occurs 

 *Use open vent or 

overflow line to 

secondary containment 

for overpressure, 

overfill and vacuum 

protection 

 *Eliminate utility 

connections above 

pressure rating of 

vessel 
Attachment C 

Inherently Safer Systems Checklist 

Date: June 15, 2011 

C-18 

No. 

Inherently Safer 

Design Alternative 

Applicable 

Y/N? 

Opportunities

/ Applications Feasibility

Current 

Status Recommendation 

 *Carrying out several 

process steps in 

separate processing 

vessels rather than a 

single multi-purpose 

vessel (to reduce the 

complexity and 

number of raw 

materials, utilities, and 

auxiliary equipment 

connected to a specific 

vessel) 

Can passive leaklimiting technology be 

used to limit potential 

loss of containment? 

 *Blowout resistant 

gaskets (e.g., spiral 

wound) 

 *Increasing wall 

strength of piping and 

equipment 

 *Maximize use of allwelded pipe 

 *Using fewer pipe 

seams and joints 

 *Providing extra 

corrosion/erosion 

allowance (e.g., Sch. 80 

vs. 40) 

 *Reducing or 

eliminating vibration 

(e.g., through vibration 

dampening or 

equipment balancing) 

4.2 

 *Minimizing the use 

of open-ended (bleed 

or vent), quick -

opening valves (for 

example, quarter-turn 

ball or plug valves) 
Attachment C 

Inherently Safer Systems Checklist 

Date: June 15, 2011 

C-19 

No. 

Inherently Safer 

Design Alternative 

Applicable 

Y/N? 

Opportunities

/ Applications Feasibility

Current 

Status Recommendation 

 *Eliminating the use 

of open-ended (bleed 

or vent), quick -

opening valves (for 

example, quarter-turn 

ball or plug valves) in 

hazardous service 

 *Using incompatible 

hose connections to 

prevent misconnection (e.g., 

air/nitrogen, raw 

materials) 

 *Use of round valve 

handles for open 

ended quarter-turn 

valves to minimize 

potential for bumping 

open 

 *Improving valve 

seating reliability (e.g., 

using system pressure 

to seal valve seats 

where possible, using 

valve seat geometry, 

valve operations, and 

flow to eliminate or 

reduce seat damage) 

 *Eliminating 

unnecessary expansion 

joints, hoses, and 

rupture disks 

 *Use of articulated 

arms instead of hoses 

for loading/unloading 

of hazardous materials 

 *Eliminating 

unnecessary sight 

glasses/glass 

rotameters; use highpressure/armored 

sight glasses as needed 
Attachment C 

Inherently Safer Systems Checklist 

Date: June 15, 2011 

C-20 

No. 

Inherently Safer 

Design Alternative 

Applicable 

Y/N? 

Opportunities

/ Applications Feasibility

Current 

Status Recommendation 

 *Eliminate use of 

glass, plastic or other 

brittle material as 

material of 

construction 

 *Use of seal-less 

pumps (e.g., canned, 

magnetic drive) 

 *Minimizing the 

number of different 

gaskets, nuts, bolts, 

etc. used to reduce 

potential for error 

4.3 Are there any other 

alternatives for 

simplifying operations 

involving hazardous 

materials in this 

process? 

5.0 LOCATION/SITING/

TRANSPORTATION 

5.1 Can the plant be 

located to minimize 

the need for 

transportation of 

hazardous materials? 

(e.g., co-located with 

supplier/customer, onsite production of 

hazardous raw 

materials) 

Can hazardous process 

units be located to 

eliminate or minimize: 

 *Adverse effects from 

adjacent hazardous 

installations 

5.2 

 *Off-site impacts 
Attachment C 

Inherently Safer Systems Checklist 

Date: June 15, 2011 

C-21 

No. 

Inherently Safer 

Design Alternative 

Applicable 

Y/N? 

Opportunities

/ Applications Feasibility

Current 

Status Recommendation 

 *On-site impacts on 

employees and other 

plant facilities including 

control rooms, fire 

protection systems, 

emergency response 

and communication 

facilities, and 

maintenance and 

administrative facilities 

5.3 Can a multi-step 

process, where the 

steps are done at 

separate sites, be 

divided up differently 

to eliminate the need 

to transport hazardous 

materials? 

5.4 Can materials be 

transported: 

 *In a less hazardous 

form (e.g., refrigerated 

liquid vs. pressurized) 

 * In a safer transport 

method (e.g., via 

pipeline, top-vs. 

bottom-unloaded, rail 

vs. truck) 

 *Along a safer route 

(e.g., avoiding high risk 

areas such as high 

population areas, 

tunnels, or highaccident-rate sections 

of roadway)? 

 

1Center for Chemical Process Safety, “Inherently Safer Chemical Processes: A Life Cycle Approach,” CCPS, 

AIChE, New York, Second Edition, 2009 
Attachment C 

Inherently Safer Systems Checklist 

Date: June 15, 2011 

C-22