Post0218 T-ZONES & LTP 18 January 2000
CONTENTS
1. T-ZONES AND LOW TEMPERATURE PROTECTION
2. VACCINE FREEZING AND FROST FREE REFRIGERATORS, CONTINUED
3. REFRIGERATOR TEMPERATURE RANGE 2'C TO 8'C?
4. SOLUTION SUGGESTION FOR VACCINE FREEZING
1.T-ZONES AND LOW TEMPERATURE PROTECTION
Hans Everts, WHO/V&B, who was, unfortunately, unable to attend the
Technet'99 meeting in Harare continues his update on outstanding Technet
issues. This continues from TECHNET post0217 Fast Chain, 17 January 2000.
Temperature regulation, LTP, and T-Zone testing, were discussed in TECHNET
Post0123, T-ZONES & LTP & VVM, 12 March 1999, and continued the the
discussions from Post0117, Post0116, Post0113, Post0111, Post0107 LTP,
Post0104, and Post0102.
Temperature zones [T-Zones] and low temperature protection for cold chain
equipment specifications were agreed in principle at the Technet'98 meeting
in Copenhagen. Hans, Terry Hart ITG/India, Anthony Battersby, FBA, and
Allan Bass acted as a working group for this issue, with Hans also acting
for the Technet Secretariat at WHO.
In yesterdays TECHNET Post:
" On other matters: You had planned to have the new PIS at the printers
in December 1999. Is that done? I hope not - we did not discuss the need
for mandatory low temperature protection - specifically 0'C cutouts.
Soren Spanner posted something on that last week. I join him in feeling
that this is an urgent matter."
"regards,
allan"
Two files on the Temperature Zones are available for download via the web:
ftp://ftp.acithn.uq.edu.au/Technet/1-ClickHereForTECHNETfiles/Coldchain/
Click on the files:
NewTzonesJan2000.PDF details the proposed Temperature zones
Diurnalcycle-xls.PDF contains the spreadsheet calculations of the dirunal
cycle and world coverage.
or get the file by by email to: [[email protected]][email protected][/email]
with the message:
get technet NewTzonesJan2000.PDF
get technet Diurnalcycle-xls.PDF
Action, comments and additions please: [[email protected]][email protected][/email]
or use your reply button
___________________________________________________________________________
From: [[email protected]][email protected][/email]
Date: Fri, 07 Jan 2000 15:16:53 +0100
To:
Cc: [[email protected]][email protected][/email]
Subject: T-Zones and Low Temperature protection
Don't worry, work on the PIS will start in 2 weeks and take about 3 months.
We have hired a person to work only on that.
I agree the zero cut off need to be discussed, but I do not think that is
an issue for the PIS, but for the specifications.
We should have at some stage a smaller meeting to see what we do with the
domestic refrigerator issue.
I have made some progress on the temperature zones. Especially the
calculation of the diurnal cycle has taken some time.
Please post the attached files for comments.
The determination of the diurnal cycle is based on the CD ROM of the World
Meteorological Organization, with more than 30 000 data over the last 30
years.
THE DIURNAL CYCLES PROPOSED ARE:
Hot Zone: 43 - 25
Temperate Zone: 32 - 15
Cold Zone: 32 - 15 and 15 - minus 5
* For those who are interested, the calculation was done as follows:
The WMO database provides for all stations the mean maximum and minimum
temperature per month over 30 years. I have taken the difference between
these 2 as the basis for the computation of the diurnal cycle. I did not
attach the WMO file, because its size is 13 MB (Anthony, if you want I can
send it to you).
The average of all these differences gives the average diurnal cycle, which
is of course not enough, since an average itself does not tell anything
about the spread of the data.
I assumed a normal distribution of the data, which turns out to be not far
from the truth as can be shown in the small difference between the mean and
the median.
In a normal distribution the average plus/minus 2 times the standard
deviation covers 95% of the measurements. Let's call this the diurnal
interval. With an upper limit of 43?C or 32?C, the lower limit can then be
determined by taking the diurnal interval (average difference plus twice
the standard deviation) off.
As you can see in the Excel file, this gives for all stations a lower test
point of 24.77?C for the hot zone and 13.77?C for the temperate zone. If we
would, for the sake of standardization, use 25?C and 15?C, we would still
cover respectively 94.88% and 92% of the measurements for all stations.
However, as you can see, the difference between maximum and minimum in
Africa is bigger than elsewhere. To cover 95% we would have to take 22.57?C
and 11.6?C as lower test points, which is a few degrees from the currently
used standards. You can see that if we would use 25?C and 15?C we would
only cover 84.44% and 76.6%, which as such would not be enough. I do not
think we should go lower than 90%.
However, there is an over-estimation in the calculations for 2 reasons:
1) the mean maximum and the mean minimum do not necessarily and probably
will not often fall on the same day;
2) appliances are not directly exposed to the extremes of the diurnal
cycle, which concerns outside temperatures. The fact that they are
installed inside [a building] has an attenuating effect.
I have assumed an attenuation of 3?C, which I think is not exaggerated. The
last column shows the percentages of measurements covered, when an
attenuation of 3?C is included, while respecting the lower limits of 25?C
and 15?C. Even in Africa this brings the number of measurements covered
easily above the 90%.
To conclude therefore, I think it is justified to use in the [cold chain
equipment] specifications, from now on, the diurnal cycles 43?C-25?C and
32?C-15?C, since this interval covers at least 95% of all measurements.
regards,
Hans
---
From:
Date: Fri, 14 Jan 2000
To: [[email protected]][email protected][/email]
Cc: [[email protected]][email protected][/email]
Subject: T-Zones and Low Temperature protection
Dear Hans,
Thanks! The Fast Chain posting should go out today or Monday. Thanks for
doing all of the work on it. If I have any questions - I'll put it in the
Technet post as well as email to your for your thoughts.
* We do need to discuss the zero cut off specifications - and testing
procedures. I suggest we draft something and put it to the forum in the
next few weeks. I know there is a lot of grumbling because this has been on
the agenda for so long without any action.
After safe injections and VVMs, low temperature protection is, perhaps the
key cold chain equipment issue relating to program cost effectiveness - in
terms of human costs, vaccine costs, opportunity costs, and energy costs.
* The reason I mentioned the PIS - it that I think that the advice on Low
Temperature Protection should be in the PIS - as the cold chain reference
manual - which is how it is used! (Glad you have some help on the PIS)
* The other thing noted recently - is that some countries are using
commercially marketed domestic picnic ice packs - which usually have
additive salts and polymers to depress the melting point - increasing the
potential for vaccine freezing. You will recall that WHO has the test
reports on cold packs from the late 70's/early 80's. I think that these
need to be re-issued - perhaps through the PIS.
more later,
regards and best wishes,
allan
____________________________________*______________________________________
2. REFRIGERATOR TEMPERATURE RANGE 2'C TO 8'C?
The current WHO recommendation for EPI vaccine storage in refrigerators is
for one month at 0 'C to +8'C. Other regions of the world and other
countries recommend +2'C, or even +4'C to 8'C. Many manufacturers label
their vaccine vial for storage between 0'C and 10'C.
* Mary Catlin, PATH, proposes, considering the risk of zero degree storage
on HepB - a vaccine coming into wide routine use, that we try to modify the
recommendation to +2'C to Plus 8'C on the TECHNET Forum.
The slop and hysteresis inherent in the cheap mechanical refrigerator
thermostats that are in most refrigerators makes the 0'C recommendation a
danger to freeze sensitive vaccines.
Action, comments and additions please: [[email protected]][email protected][/email]
or use your reply button
___________________________________________________________________________
From: "Catlin, Mary"
To: "'Technet Moderator'"
Subject: RE: Refrigerator temperature range 2-8 C
Date: Fri, 14 Jan 2000 12:47:36 -0800
Bob Davis of UNICEF brought to my attention that some EPI materials
and country programs recommend keeping refrigerators at 0-8 degrees C, not
2-8 degrees C.
Since hepatitis B vaccine freezes at -0.5 C, and may be introduced in new
countries in the coming years, I wonder if Technet members would
support a recommendation to WHO and UNICEF that refrigerator temperatures
be kept at 2-8 C?
Thank you,
Mary
Mary Catlin
Program Officer
Program for Appropriate Technology in Health (PATH)
4 Nickerson Street
Seattle, WA 98109-1699
USA
Tel: (206)285-3500 Fax: (206-285-6619)
E-mail:[email protected]
____________________________________*______________________________________
3. VACCINE FREEZING AND FROST FREE REFRIGERATORS, CONTINUED
In Post0212, VACCINES & COLD CHAIN, 26 November 1999 Anthony Battersby,
FBA, raised the issue of the risk of vaccine freezing in 'Frost Free'
refrigerators which have sub-zero temperatures in some parts of the
refrigerator cabinet. The discussion continued in Post0214, VACCINE
FREEZING,on 07 January 2000.
Hepatitis-B vaccine has a melting point of -0.5'C, while other freeze
sensitive vaccines freeze between 0'C and -4'C.
See posts 3 and 4 in this TECHNET Forum posting for other related issues.
Action, comments and additions please: [[email protected]][email protected][/email]
or use your reply button
___________________________________________________________________________
Date: Fri, 7 Jan 2000 08:52:33 -0800
From: [[email protected]][email protected][/email] (Mikko Lainejoki)
Subject: Frost free refrigerators
To: [[email protected]][email protected][/email], [[email protected]][email protected][/email]
Anthony, Allan,
I have spent this week reading through old messages and found Anthony's
message on frost free refrigerators. In my opinion the message is quite an
over-exaggeration and may do more harm than good.
Even if we wanted we cannot construct a refrigerator described by Anthony
(ref. fundamentals of thermodynamics and heat transfer):
Quote
The problem is that at the point of entry into the refrigerator
cabinet this air is at -15/-20degC. The result is that the middle
part of the refrigerator may be as cold as -7DegC while the rest is at
+4DegC.
Unquote
I'm sorry to miss the Harare meeting; hope everything went well.
Best wishes for the New Year.
mikko
---
Date: Fri, 7 Jan 2000 07:06:42 -0500
From: Anthony Battersby
Subject: Frost free refrigerators
To: Mikko Lainejoki ,
Cc:
Dear Mikko,
Multiflow /frost free systems exist it is the system of choice for many
North American and Far Eastern manufacturers. I was not exaggerating just
reporting facts resulting from a field test carried out on 9 multifow
refrigerators over three months. Multiflow is risky for vaccine storage.
At Technet, Carib (I think it was), confirmed that he had had experience of
multiflow systems freezing vaccine. They are not popular in Europe
because they use much more energy, but are popular elsewhere because they
never need defrosting.
Happy New Year
Anthony
____________________________________*______________________________________
4. SOLUTION SUGGESTION FOR VACCINE FREEZING
Carl Erickson, Solar Ice Company, offers this solar solution, applicable in
certain situations.
Action, comments and additions please: [[email protected]][email protected][/email]
or use your reply button
___________________________________________________________________________
From: [[email protected]][email protected][/email]
Date: Fri, 7 Jan 2000 13:00:00 EST
Subject: Solution Suggestion for Vaccine Freezing
To: [[email protected]][email protected][/email]
January 7, 2000
Dear Technet Subscribers:
In regards to the problem of vaccine freezing - I suggest keeping vaccine
in cold boxes. Since ice at 0C provides the refrigeration, vaccine can not
freeze.
If not enough ice is available for the cold box and other uses, or if it is
costly to make or provide, I suggest using the ISAAC solar icemaker.
I am interested in hearing more about where the problem is occurring.
Information about the ISAAC can be seen in Post 195, or by contacting me.
Sincerely,
Carl Erickson
Solar Ice Company
[email protected]
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