Kenya Standard    KS 2552: 2018 
 
  
 
 
 
 
 
 
 
 
 
 
 
 
Mouth props and airways (London Hospital 
Pattern)  — Specification  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
©KEBS 201 8          First Edition 20 18 
 KS 2552: 2018 
 
ii  © KEBS 201 8 — All rights reserved  TECHNICAL COMMITTEE REPRESENTATION  
 
The following organizations were represented on the Technical Commit tee: 
 
Nursing Council of Kenya  
Ministry of Health  
Government Chemist 's Department  
Coast Provincial Hospital  
County of Nairobi  
Association for the Physically Disabled of Kenya  
Christian Health Association of Kenya (CHAK)  
Kenyatta National Hospital  
Kenya Bur eau of Standards — Secretariat  
 
 
 
 
 
 
 
 
 
 
 
REVISION OF KENYA STANDARDS  
 
In order to keep abreast of progress in industry, Kenya Standards shall be regularly reviewed. Suggestions for 
improvements to published standards, addressed to the Managing Director , Kenya Bureau of Standards, are 
welcome . 
 
 
 
 
 
 
© Kenya Bureau of Standards, 20 18 
 
Copyright.  Users are   reminded that by virtue of section 25 of the Copyright Act, Cap. 12 of 2001 of the Laws of Kenya, cop yright 
subsists in all Kenya Standards and except a s provided under section 26 of this Act, no Kenya Standard produced by Kenya Bureau of 
Standards may be reproduced, stored in a retrieval system in any form or transmitted by any means without prior permission in  writing 
from the Managing Director.  
 
 
 
 
 Kenya Standard    KS 2552: 2018 
 
© KEBS 201 8 — All rights reserved    iii  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Mouth props and airways (London Hospital 
Pattern)  — Specification  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
KENYA BUREAU OF STANDARDS (KEBS)  
 
Head Office:  P.O. Box 54974, Nairobi -00200, Tel.: (+254  020) 605490, 602350, Fax: (+254 020)  604031  
E-Mail: info@keb s.org,  Web:http://www.kebs.org  
 
Coast Region     Lake Region          Rift Valley Region  
P.O. Box 99376, Mombasa -80100   P.O. Box 2949, Kisumu -40100        P.O. Box 2138, Nakuru -20100  
Tel.: (+254  041) 229563, 230939/40  Tel.: (+254 057) 23549, 22396        Tel.: (+254 051) 210553, 210555  
Fax: (+254  041) 229448    Fax: (+254 057) 21814  
 KS 2552: 2018 
 
iv  © KEBS 201 8 — All rights reserved  Foreword  
 
Kenya Bureau of Standards is a national standards bod y (NSB). The work of preparing Kenya  Standards is 
normally carried out through national  technical committees. Each  member body interested in a subject for 
which a technical committee has been established has the right to be represented on that committee. National  
organizations, governmental and non -governmental, in liaison with KEBS , also take part in the work.  
Kenya  Standards are drafted in accordance with the rules given in the KS ISO/IEC  Directives, Part  2. 
The main task of technical committees is to prepare National  Standards. Draft Kenya  Standards adopted by 
the technical committees are circulated to the technica l committee member s for ballo ting. Publication as a 
Kenya  Standard requires approval by at least 2/3 of the member s casting a vote.  
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent 
rights. KEBS  shall not be held responsible for identifying any or all such patent rights.  
This Kenya Standard  was prepared by Technical Committee KEBS /TC 136, Medical Tools, devices and 
Equipment . 
During the development of this standard , reference was made to the follow ing document:  
 
IS: 3393 -1965 Mouth props and airways (London hospital pattern) . 
 
This assistance is hereby highly acknowledged . 
 
 
 
 
  
Kenya Standard    KS 2557: 2018 
 
 
© KEBS 201 8 — All rights reserved    1  
 
 
Mouth props and airways (London Hospital Pattern)  — Specification  
 
 
 
1 Scope  
 
This Kenya National Workshop Agreement standard covers the requirements for mouth props and airways 
(London Hospital Pattern).  
 
2 Shape and dimensions   
 
2.1 The general shape, dimensions and range of nominal sizes of mouth props and airways (London 
 Hospital Pa ttern) shall be as given in Figure  1 and Table 1.  
 
 
Table 1 — Dimensions of mouth props and airways  
(Clause 2.1)  
 
 
Size H A B C 
Large  30 35 25 15 
Medium  25 28 22 12 
Small  20 22 19 10 
 
 
 
 
2.2 The mouth props shall be of the following three sizes:  
 
a) Large   15 mm  
 
b) Medium  12 mm  
 
c) Small   10 mm  
 
2.3 Each mouth prop shall be provided with a 1.6 -mm hole at th e base to allow it to be used  with a chain 
or a wire.  When specifically required, three mout h props, one of each size,  shall be supplied together as a 
set, in which case they shall be linked by means of aluminimum chains approximately 15 cm long with links 
made of 1 mm diameter aluminimum wire.  
 
3 Material  
 
The mouth props and airways shall be manufactured from a corrosion -resisting metal or a metal finished with 
durable and corro sion resisting surface coating.  The material used shall be in no way harmful to human 
tissue. Aluminium, stainless steel and carbon steel (chromium plated) are suitable materials for these mouth 
props and airways.  The mouth props may be made also from suitable  elastomeric materials.  
 
4 The surface of the mouth props and airways shall be smooth and free from pits, s cratches, and 
grinding marks. The edges shall be smoothly rounded off and shall nowhere be sharp.  If plated, the plating 
shall be chromium over nicke l conforming to Annex A.  
 KS 2552: 2018 
 
2  © KEBS 201 8 — All rights reserved  5 Test 
 
5.1 Practical t est  
 
A compressive force of 25 kgf shall be applied to each mouth prop in turn in such a maaner that the force acts 
at right angles to the axis and throug h its mid point and tends to compress the opposite s urfaces towards 
each other . The maximum force shall gradually be attained and swhll act for two minutes.  On completion of 
the test the mouth props sha ll not have taken on a new permanent s hape  and shall show no sign of damage.  
 
6 Marking  
 
6.1 Each mouth prop shall be legibly and indelibly marked with the manufacturer’s name, initials or 
recongnized trade -mark and the year of manufacture.  
 
6.1.1  The mouth props and airways may also be marked with the S -Certification Mark.  
 
NOTE  The use of the S -Certificat ion Mark is governed by the provisions of the Kenya Bureau of Stand ards 
(Certification Marks) , and the Rules a nd Regulatins made thereunder. Presence of this mark on products 
covered by a  Kenya  Standard conveys the  assurance that  they have been produced to  comply with the 
requirements of th at standard, under a well -defined system of inspeciton, testing and qual ity control during 
production. This system, which  is devised and supervised by KEBS  and operated by the  producer, has the 
further safe g uard that the  products as actua lly marketed are continuously checked by KEBS  for conformity to 
the stanard.  Details of conditions, under which a licence for the use of S - Certfidicatin Mark may be granted to 
manufacturers or processors, may be obtained from the  Kenya B ureau of Standards . 
. 
7 Packing  
 
7.1 The mouth props and airways shall be wrapped in suitable material and  packed in cardboard boxes 
or cartons.  
 
7.2 A label shall be fixed on each carton indic ating the manufcturer’ s name, initials or trade mark.  
 Kenya Standard    KS 2552: 2018 
 
© KEBS 201 8 — All rights reserved    3 Annex  A 
(normative)  
 
Specification for nickel -chromium deposits in stethosc opes 
 
A.1 Nickel deposit  
 
A.1.1  The type of nickel shall be indicated by the following symblols placed after the chemical symbol  Ni 
followed by figures denoting thickness of nickel depos it. 
 
‘b’ for nickel deposited in  fully bright condition. This type of deposit usually  contains a little  
 sulphur  derived from brighteners.  
 
‘p’ for dull or semi -bright nickel requiring polishing to give ful l brightness, containing less than 0.005 
%  sulphu r1, and passing the ductility test given in KS ISO 8401:1986.  
 
‘d’ for a double -layer nickel coating, of which the bottom l ayer contains less that 0.005 % sulphur3) and 
passes the ductility test given in KS ISO 8401:1986 and the top layer contains more tha n 0.04 % 
sulphur3); the thickness of the bottom and top layers shall not be less than 60 percent and 20 percent 
respe ctively of the total nickel thickness..  
 
A.1.2  Thickness of nickel deposit   
 
This is specified in microns and denotes the minimum thickness  of the nickel measured by the stripping 
method given in KS ISO 1461  which shall be present at any point of the significant surface that may be.  
 
A.2 Chromium deposit  
 
A.2.1  The type of chromium deposit shall be designated by the follo wing symblols placed after the chemical 
symbol Cr;.  
 
‘r’ for regular or common type of chromium having a minimum thickness of 0.3 micron.  
 
‘f’ for chromium free from cracks, when checked by the microscopic method (except for cracks extending 
from the edges of the component to 25 % of the width of the component or 10 mm whichever is the less) 
and havin g a minimum thickness of 0.8 micron.  
 
A.2.2  Thickness of chromium deposit   
 
This is specified in microns and denotes the minimum thickness of the chromium deposit, measured by the  
stripping  method given in KS ISO 1461, which shall be present at any point of the significant surface that may 
be touched  by a ball 20 mm in diameter.  
 
A.2.3  Example of complete classificatin number  
 
For example, ‘S Ni40b Cr r’ shall denote a coating on steel consisting of 40 microns (minimum) of bright nickel 
followed by 0.3 micron (minimum) regular chromium.  
 
A.2.4  Coatings appropriate to each service grade number   
 
                                                           
1 The sulphur contents are specified in order to indicate the t ype of nickel platin g solution that is to be used. No simple method exists for 
determining the sulphur content of a nickel deposit on a coated article An accurate determination is possible on a specially prepared 
test specimen.  
 KS 2552: 2018 
 
4  © KEBS 201 8 — All rights reserved  Table 1 gives the Classification Numbers corresponding to each Service Grade Number for nickel -chromium 
plating on iron and steel.  
 
Table 1 — Nickel -chromium plating on iron and steel  
 
 
 
  Servicer Grade No.     Classification No  
 
   4     S Ni40p Cr r  
        S Ni40d Cr r  
        S Ni40d Cr.f  
 
        S Ni40b Cr r  
        S Ni30p Cr r  
   3     S Ni30d Cr.r  
        S Ni30d Cr.r  
   2*     S Ni20b Cr.r  
   1*     S Ni10b Cr.r  
 
*p- or d-nickel and f -chromium may be substituted for b -nickel and r -chromium in Service Grade Numbers 2 
and 1. 
 
 
 
A.3 Adhesion  
 
Adhesion  of the coating  shall be tested by the method given in KS ISO 4522 -2. The coating should continue 
to adhere to the basis metal when subjected to this test.  
 
A.4 Corrosion resistance   
 
The plated article should be subjecyted for the specified duration to one of the corrosion tests shown i n Table 
2 to be appropriate for the particular Service Grade Number .  The coating shall not show appreciable 
corrosion as indicated by the development of rust spots.  Unless other wise agreed between the purchaser 
and the supplier, appreciable corrosion sh all be defined as the presence of more thant two corrosion spots 
per square decimeteres and not more than 10 corrosion spots in asny single area covering 25 cm2, as seen 
with the naked eye.