ASHRAE Journal - April 2023 - 56
REFRIGERATION APPLICATIONS
COLUMN
Andy Pearson
Nontoxic?
BY ANDY PEARSON, PH.D., C.ENG., FELLOW ASHRAE
I have been delving into the art of risk assessment for industrial refrigeration systems
and unearthed some surprising and interesting quirks. Here are a few anomalies that
help keep the daily workload interesting. I preface this column with a disclaimer that
I am not suggesting that we abandon safe working practices-just sayin'.
The international standard ISO 817:2014 recognizes
two classes of refrigerant toxicity, described in clause
6.1.2 of the standard as " lower chronic toxicity " (class
A) and " higher chronic toxicity " (class B). ASHRAE
Standard 34-2022 defines toxicity as " the ability of
a refrigerant to be harmful or lethal due to acute or
chronic exposure by contact, inhalation or ingestion "
and goes on to say " For this standard, temporary discomfort
at a level that is not impairing is excluded. " ISO
817 doesn't have a definition of toxicity but it
does define acute toxicity as " adverse health
effect(s) from a single short-term exposure "
and chronic toxicity as " adverse health
effect(s) from long-term repeated exposures. "
The puzzle is that study of cause and effect
in dozens of documented serious industrial
refrigeration accidents showed that when
fatal accidents occur with ammonia the casualties
are almost always within a few feet of
the point of release. However, the traditional methods
of analyzing the consequences of ammonia releases
don't seem to acknowledge this and use calculation
techniques more suited to other chemical hazards.
Looking more deeply into references on ammonia toxicity,
I found that there are no chronic toxic effects and
the threshold level for serious permanent injury from
inhalation was more than 1,500 ppm. So why would it
be classed as " higher chronic toxicity " by ISO 817?
The threshold limit value (TLV) for long term exposure
to ammonia is low because it has such an irritating
reaction with moist body parts (eyes, nose, throat) that
the occupational exposure limit (OEL) is therefore typically
set in workplace regulations as 25 ppm. This value
assigns it to class B in ISO 817, but this has nothing to do
with toxicity; it is what Standard 34 calls " temporary
56
ASHRAE JOURNAL ashrae.o rg
A P R I L 2023
Refrigerant classification is
complicated.
discomfort at a level that is not impairing, " an effect
supposedly excluded from the classification process.
This reminded me of my favorite refrigerant safety
joke (credit to Professor Joachim " Joe " Paul, former head
of IIR's Science and Technology Council): Joe was a great
proponent of the use of water as a refrigerant in vapor
compression systems, but he always gave the stern
warning that water was obviously the most hazardous
refrigerant " because it's the only one that contains
sharks. " There is a serious point behind Joe's
quip: the assessment of risk has to be relevant
to the circumstances. Suitable metrics
and methods need to be used, otherwise the
conclusions reached will be inappropriate
and possibly even counter-productive.
In the case of ammonia risk assessments,
the client needs to be clear about the objective.
Worker safety should be paramount
and leads to a number of key requirements
in training, managing and equipping staff. Comfort and
convenience for the surrounding community is also a
relevant objective but requires a different set of measures
and is not really a safety concern; it is more about
being a good neighbor. Measures that ensure neighbor
comfort will not guarantee worker safety and vice versa.
I worked on this puzzle with Alex Pachai, chair of the
IIR's Safety Working Group and Kent Anderson, former
president of IIAR, following a safety workshop held a
year ago at the IIR's Cold Chain conference. We hope to
present the findings in a series of papers in Paris later
this year. Meanwhile, ISO 817 is currently being revised
and the anomaly about chronic toxicity mentioned
above will hopefully be resolved.
Andy Pearson, Ph.D., C.Eng., is group managing director at Star Refrigeration in
Glasgow, UK.
ISTOCKPHOTO/ ALEXYZ3D
http://ashrae.org
ASHRAE Journal - April 2023
Table of Contents for the Digital Edition of ASHRAE Journal - April 2023
Contents
ASHRAE Journal - April 2023 - Cover1
ASHRAE Journal - April 2023 - Cover2
ASHRAE Journal - April 2023 - 1
ASHRAE Journal - April 2023 - Contents
ASHRAE Journal - April 2023 - 3
ASHRAE Journal - April 2023 - 4
ASHRAE Journal - April 2023 - 5
ASHRAE Journal - April 2023 - 6
ASHRAE Journal - April 2023 - 7
ASHRAE Journal - April 2023 - 8
ASHRAE Journal - April 2023 - 9
ASHRAE Journal - April 2023 - 10
ASHRAE Journal - April 2023 - 11
ASHRAE Journal - April 2023 - 12
ASHRAE Journal - April 2023 - 13
ASHRAE Journal - April 2023 - 14
ASHRAE Journal - April 2023 - 15
ASHRAE Journal - April 2023 - 16
ASHRAE Journal - April 2023 - 17
ASHRAE Journal - April 2023 - 18
ASHRAE Journal - April 2023 - 19
ASHRAE Journal - April 2023 - 20
ASHRAE Journal - April 2023 - 21
ASHRAE Journal - April 2023 - 22
ASHRAE Journal - April 2023 - 23
ASHRAE Journal - April 2023 - 24
ASHRAE Journal - April 2023 - 25
ASHRAE Journal - April 2023 - 26
ASHRAE Journal - April 2023 - 27
ASHRAE Journal - April 2023 - 28
ASHRAE Journal - April 2023 - 29
ASHRAE Journal - April 2023 - 30
ASHRAE Journal - April 2023 - 31
ASHRAE Journal - April 2023 - 32
ASHRAE Journal - April 2023 - 33
ASHRAE Journal - April 2023 - 34
ASHRAE Journal - April 2023 - 35
ASHRAE Journal - April 2023 - 36
ASHRAE Journal - April 2023 - 37
ASHRAE Journal - April 2023 - 38
ASHRAE Journal - April 2023 - 39
ASHRAE Journal - April 2023 - 40
ASHRAE Journal - April 2023 - 41
ASHRAE Journal - April 2023 - 42
ASHRAE Journal - April 2023 - 43
ASHRAE Journal - April 2023 - 44
ASHRAE Journal - April 2023 - 45
ASHRAE Journal - April 2023 - 46
ASHRAE Journal - April 2023 - 47
ASHRAE Journal - April 2023 - 48
ASHRAE Journal - April 2023 - 49
ASHRAE Journal - April 2023 - 50
ASHRAE Journal - April 2023 - 51
ASHRAE Journal - April 2023 - 52
ASHRAE Journal - April 2023 - 53
ASHRAE Journal - April 2023 - 54
ASHRAE Journal - April 2023 - 55
ASHRAE Journal - April 2023 - 56
ASHRAE Journal - April 2023 - Cover3
ASHRAE Journal - April 2023 - Cover4
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_FYONLJ
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_amca_2024november_v2
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_amca_2024november
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_BDMHLG
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_WJDGRY
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_ATMAHK
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_VHQRAW
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_XGMDXI
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_YELQLJ
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_QJLWMC
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_MCDEBX
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_WNYSQY
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_XATVOD
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_FJSHSS
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_CCBZDS
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_XDEFVG
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_amca_2023november_v2
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_amca_2023november
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_VHGNBL
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_WPKBNJ
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_UUVCDE
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_RTGDEW
https://www.nxtbook.com/nxtbooks/ashrae/ashraemexico_2023
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_LKRFXS
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_AZSOFG
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_ERCDBH
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_QWDFRV
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_JHGVDF
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_OPUYHG
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_SREIBM
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_LRTGLK
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_OKRFGH
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_amca_2022november_v2
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_amca_2022november
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_TZSERA
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_LVRUIX
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_RPTVYZ
https://www.nxtbook.com/nxtbooks/ashrae/mini_pub_catalog
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_XIYTGD
https://www.nxtbook.com/nxtbooks/ashrae/ashraemexico_2022
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_RFGDOB
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_PABXNU
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_REMKLS
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_PICVBT
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_AOYTVW
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_JQOPLS
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_IOYTBC
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_SGAJJF
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_IGHYER
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_PDRKLS
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_amca_2021november
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_amca_2021november_v2
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_XCODFR
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_QSLFGO
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_ILKVNM
https://www.nxtbook.com/nxtbooks/ashrae/ashraemexico_2021
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_OPDJKD
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_VJKSRY
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_SDHUTC
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_JPPKRR
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_SDLTTH
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_CKLLES
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_SLDOX
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_HJETUK
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_OLUHGE
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_amca_2020october
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_amca_2020october_v2
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_ZERDGH
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_QVMNEO
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_RTPOKE
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_BBATRE
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_STUBMW
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_TPEMPE
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_JNMKDS
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_FBTTPA
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_WQMMNE
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_TVBRYN
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_showguide2020
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_KTUZMA
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_ABEDGD
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_201910
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_201909
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_amca_2019septmeber_v2
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_amca_2019september
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_201908
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_201907
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_201906
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_201905
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_201904
https://www.nxtbook.com/nxtbooks/ashrae/meetingplanner_2019april
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_201903
https://www.nxtbook.com/nxtbooks/ashrae/meetingplanner_2019march
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_201902
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_201901
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_showguide2019
https://www.nxtbook.com/nxtbooks/ashrae/meetingplanner_2018december
https://www.nxtbook.com/nxtbooks/ashrae/meetingplanner_2018november
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_amca_2018fall_v2
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_amca_2018fall
https://www.nxtbook.com/nxtbooks/ashrae/meetingplanner_2018october
https://www.nxtbook.com/nxtbooks/ashrae/ashraemexico_2018
https://www.nxtbook.com/nxtbooks/ashrae/meetingplanner_201810
https://www.nxtbook.com/nxtbooks/ashrae/ashraeinsights_201806
https://www.nxtbook.com/nxtbooks/ashrae/meetingplanner_201805
https://www.nxtbook.com/nxtbooks/ashrae/meetingplanner_201804
https://www.nxtbook.com/nxtbooks/ashrae/meetingplanner_201803
https://www.nxtbook.com/nxtbooks/ashrae/meetingplanner_201712
https://www.nxtbook.com/nxtbooks/ashrae/meetingplanner_201711
https://www.nxtbook.com/nxtbooks/ashrae/meetingplanner_201710
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_amca_2017fall_v2
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_amca_2017fall
https://www.nxtbook.com/nxtbooks/ashrae/meetingplanner_201709
https://www.nxtbook.com/nxtbooks/ashrae/meetingplanner_201705
https://www.nxtbook.com/nxtbooks/ashrae/ashrae_meetinginsert_201610
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_amca_2016fall_v2
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_amca_2016fall
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_acrexindia
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_amca_2015summer_v2
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_amca_2015summer
https://www.nxtbook.com/nxtbooks/amca/2014summer2
https://www.nxtbook.com/nxtbooks/amca/2014summer
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_acma_2014summer
https://www.nxtbook.com/nxtbooks/ashrae/meetingplanner_201311
https://www.nxtbook.com/nxtbooks/ashrae/meetingplanner_201309
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_acmasupp_2013fall
https://www.nxtbook.com/nxtbooks/ashrae/meetingplanner_201305
https://www.nxtbook.com/nxtbooks/ashrae/meetingplanner_201303
https://www.nxtbook.com/nxtbooks/ashrae/pubcatalog_2013winter
https://www.nxtbook.com/nxtbooks/ashrae/meetingplanner_201211
https://www.nxtbook.com/nxtbooks/ashrae/achr_expo_mexico2012
https://www.nxtbook.com/nxtbooks/ashrae/meetingplanner_201209
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_201208_v3
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_201208_v2
https://www.nxtbook.com/nxtbooks/ashrae/pubcatalog_2012summer
https://www.nxtbook.com/nxtbooks/ashrae/meetingplanner_201205
https://www.nxtbook.com/nxtbooks/ashrae/meetingplanner_201203
https://www.nxtbook.com/nxtbooks/ashrae/pubcatalog_2012winter
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_201111_v2
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_201109_v2
https://www.nxtbook.com/nxtbooks/ashrae/pubcatalog_2011summer
https://www.nxtbook.com/nxtbooks/ashrae/meetingplanner_201105
https://www.nxtbook.com/nxtbooks/ashrae/meetingplanner_201103
https://www.nxtbookmedia.com