DKS 2924:2020  
                                   © KEBS 2020 – All rights reserved  DRAFT KENYAN  STANDARD              [ ICS XX; XXX ] 
    
                                         First [Edition]   
          
 
 
 
 
 
 
 
 
 
 
Personal Protective Equipment - Face Masks – Masks for 
public use - Requirements a nd Test Methods  
   
  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
  DKS 2924:2020             
© KEBS 2020 – All rights reserved    2 
 Technical Committee Representation  
 
The following organizations were represented on the Technical Committee  
 
Alpha Medical Manufacturers Limited  
Association of  Medical Engineers of Kenya(AMEK)  
Christian Health Association of Kenya(CHAK)  
Diverse Management Consultancy Ltd  
Equra Health Kenya  
Gertrude's Children's Hospital  
Jads Diagnostics EA Ltd  
Kenya Medical Supplies Agency (KEMSA)  
Kenya Accreditation Service (KENAS)  
Kenya National Chamber of Commerce and Industry (KNCCI)  
Medtronics Kenya  
Ministry of Health  
Physicist Society of Kenya  
Sub county Health Services, Kamukunji  
Kenya Bureau of Standards (KEBS) - 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, 2020  
Copyright. Users are reminded that by virtue of Section 25 of the Copyright Act, Cap. 130 of 2001 of the Laws of Kenya, copyr ight subsists 
in all Kenya Standards and except as provided under Section 25 of this Act, no Kenya Standard produced by Kenya Burea u of Standards 
may be reproduced, stored in a retrieval system in any form or transmitted by any means without prior permission in writing f rom the 
Managing Director.  
 
 
 
 
 
 
 
 
 
 
                                                                                                                                               DKS 2924:2020  
 
© KEBS 2020 – All rights reserved                                                                                  3  
 
 
 
 
 
 
 
 
 
 
 
Personal Protective Equipment - Face Masks – Masks for 
public use - Requirements a nd Test Methods  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
KENYA BUREAU OF STANDARDS (KEBS)  
 
Head  Office:  P.O. Box 54974, Nairobi -00200 Tel.: (+254  020) 502210 -19, 502543/45,Fax: (+254 020)  503293  
E-Mail: info@kebs.org,  Web:http://www.kebs.org   
Coast Regional Office    Western Kenya Regional Office     Rift Valley Regional Office  
P.O. Box 99376, Mombasa -80100   P.O. Box 2949, Kisumu -40100        P.O. Box 8111, Eldoret -30100  
Tel.: (+254  041) 229563, 230939/40  Tel.: (+254 057) 23549, 22396        Tel.: (+254 053) 331 51, 63377  
Fax: (+254  041) 229448    Fax: (+254 057) 21814              Fax: (+254 053) 33150  DKS 2924:2020             
© KEBS 2020 – All rights reserved    4 
   
P R E F A C E  
 
This Kenya Standard was prepared by the Technical Committee on Towels, Hygienic and Medical Textile 
Products under the guidance of the Project  Standards Committee and in accordance with standards 
development procedure . 
 
Kenyans have expressed confusion on whether or not to wear face masks in the advent of the Covid -19 
pandemic. Advice on the matter has been inconsistent, with health experts and the World Health Organization  
earlier advising that people leave the masks to medics and others on the Covid -19 frontline.  
 
However, unfolding research findings points to the contrary. I t is now clear that wearing a mask is crucial in 
protecting oneself from a virus that has infected more than one million people worldwide and killed more than 
three people in Kenya alone -including a six-year-old. The Ministry of health recently announced t hat wearing 
of masks shall be mandatory for all travelers , signaling  a major policy shift. This position was also pinned by a 
meeting convened by the Kenya Bureau of Standards and the Kenya Association of Manufacturers, where a 
section of participants made  very strong case on the use of woven material in the manufacturing of face masks.  
 
Center for Disease Control (CDC), citing new data that shows high rates of transmission from people who are 
infected but show no symptoms, now advises that the earlier guid ance on mask -wearing is “being critically re -
reviewed to see if there’s potential additional value for individuals that are infected or individuals that may be 
asymptomatically infected”.  
 
Kenya’s guidelines are limited to passenger service vehicles, boda -bodas and tuktuks, but it still brings to the 
public domain a major tool in the war against the coronavirus that has been previously ignored, and which 
could prove a game changer in the coming days. The current standard, KS 26 36 does not address the woven 
materials and other materials for use by the public inundating the develop ment of  this edition.  
 
 
During the  preparation of this standard,  reference was made to the following publications:  
 
 KS 2636, Surgical Masks – Specification  
 BS EN 14683, Medical face masks – requirements and test methods  
 ASTM -  
 
Acknowledgement is made for the assistance received from these sources.  
                                                                                                                                                DKS 2924:2020  
 
© KEBS 2020 – All rights reserved                                                                                  5  
KENYAN  DRAFT STANDARD  
 
Personal Protective Equipment - Face Masks – Masks for public use - 
Requirements and Test Methods  
 
 
 
 
1. SCOPE   
This Draft Kenya Standard specifies the requirements for masks for general use as prevention of  
aerosolized emissions  from person to person  in the general public . A face mask with appropriate 
microbial barrier can be effective in reducing emission of the infective agents from the nose and mouth 
of an asymptomatic carrier or a patient with clinical symptoms.  
 
2. Normative  references  
The following documents, in whole or in part, are normatively referenced in this document and are  
indispensable for its application. For dated references, only the edition cited applies. For undated 
references,  the latest edition of the referen ced document (including any amendments) applies.  
 
EN ISO 10993 -1, Biological evaluation of medical devices — Part 1: Evaluation and testing within a 
risk management process (ISO 10993 -1) 
 
EN ISO 10993 -5, Biological evaluation of medical devices — Part 5: Tests for in vitro cytotoxicity 
(ISO 10993 -5) 
 
EN ISO 10993 -10, Biological evaluation of medical devices — Part 10: Tests for irritation and skin  
sensitization (ISO 10993 -10) 
 
EN ISO 11737 -1, Sterilization of medical devices — Microbiological methods — Part 1: 
Determination of a  population of microorganisms on products (ISO 11737 -1) 
 
ISO 22609, Clothing for protection against infectious agents — Medical face masks — Test method 
for resistance against penetration by synthetic blood (fixed volume, horizontall y projected)  
 
3  Terms and definitions  
For the purposes of this document, the following terms and definitions apply.  
3.1 
face mask  
device covering the mouth and nose providing a barrier to minimize  the direct transmission of  infective 
agents between one person  and another  
 
Note 1 to entry: Transmission of blood -borne agents from patients to staff may occur via splashes.  
 
3.2 
bacterial filtration efficiency (BFE)  
efficiency of the medical face mask material(s) as a barrier to bacterial penetration  expressed as 
percentage.  
 
Note 1 to entry: The BFE test method is used to measure the bacterial filtration efficiency (BFE) of medical face 
mask  materials.  
 
3.3 
Filter efficiency  
The ability of the mask body to filter out particulate matter under specified conditions, expressed as 
percentage.  
 
 
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3.4differential pressure  
air permeability of the mask, measured by determining the difference of pressure across the mask 
under  specific conditions of air flow, temperature and humidity  
 
 
Note 1 to entry:  The differential pressure is an indicator of the "breathability" of the mask.  
 
 
3.4 
colony forming unit (cfu)  
unit by which the culturable number of micro -organisms is expressed  
 
Note 1 to entry: The culturable  number is the number of micro -organisms, single cells or aggregates, able to form  
colonies on a solid nutrient medium.  
 
3.5 
cleanliness  
freedom from unwanted foreign matter  
 
Note 1 to entry: Such matter can be micro -organisms, organic residues or particul ate matter.  
 
3.6 
infective agent  
micro -organism that has been shown to cause surgical wound infections or that might cause infection 
in the  patient, members of staff or other  
 
3.7 
Particulate matter  
refers to the particulate matters with air dynamics equivalent diameter less than or equal to 2.5 microns 
in the ambient air.  
 
3.8 
aerosol  
gaseous suspension of solid and/or liquid particles, the particles having a negligible falling velocity  
 
Note 1 to entry: This velocity is generally considered to be less than 0,25 m/s.  
 
3.9 
filter  
material used for mechanical and physical separation or deposition of aerosol particles (liquid or solid) 
from the inhaled and exhaled air  
 
3.10 
particle protective performance  
The ability of the mask to block particulate matter under specified conditions, expressed as a 
percentage.  
 
4. Requirements  
 
4.1.1  General  
The face mask for general public use shall not disintegrate, split or tear during intended  
use. In the selection of the filter and layer materials, attention shall be paid to cleanliness (absence of 
particulate matter).  
 
4.1.2 Visual inspection  
The visual inspection shall also include the marking and the information supplied by the manufacturer.  
 
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© KEBS 2020 – All rights reserved                                                                                  7  
 
 
4.1.3  Cleaning and disinfecting  
If the particle filtering cloth mask is designed for more than a single shift (i.e. not designed for single 
use only), the materials used shall withstand the cleaning and disinfecting agents recommended by 
the manufacturer when t ested in accordance with the method decsribed in Annex B.  
 
 
4.1.4 Design  
The face mask for general public use shall have a means by which it can be fitted closely over the 
nose, mouth and chin of the wearer and which ensures that the mask fits closely at the sides.  
Face masks shall have different shapes and constructions as shown in figure 1 (a) and (b). They may 
as well have, as additional features , a face shield (to protect the wearer against splashes and droplets) 
with or without anti -fog function, or a  nose bridge (to enhance fit by conforming to the nose contours).  
 
  
  Figure 1 (a)      Figure 1 (b)  
 
 
 
4.2 Basic requirements  
4.2.1   The mask shall be able to cover mouth and nose safely and firmly.  
4.2.2  The mask shall not be made from recycled materials and materials with high toxicity, carcinogenicity, 
or potentially carcinogenic. They shall also not be made of materials known to cause skin irritation or 
other adverse reactions. The residues of other res trictions on the material shall comply with the 
relevant requirements, no odor. 
4.2.3  Masks shall not have accessible sharp angle and edges, and shall not cause injury to the wearer.  
4.2.4  Masks shall be easy to wear and to remove, have no obvious pressure  or complications in the process 
of wearing, and shall not affect head movements.  
 
 
4.3 Performance requirements  
 
4.3.1 General  
All tests shall be carried out on finished products or samples cut from finished products, if applicable 
in their sterile  or unu sed state.  
 
4.3.2 Elastic  
The elastic material shall be synthetic elastomeric material of approximate width of 5mm. The length 
shall be such that it fits comfortably around the head or ear of the wearer.  
 
 
4.3.3 Nose piece  (optional)  
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© KEBS 2020 – All rights reserved    8 
 This, if used,  shall be flexible strips of materials of 3 mm and shall enable the mask to take the shape 
around the nose of wearer.  
 
 
 
 
4.3.5  Breathability – Inhalation resistance and exhalation resistance  
When tested in accordance with C, the differential pressure of the medical face mask shall conform to 
the value given in Table 1.  
 
4.3.4  Filter efficiency  
Masks shall have filter efficiency levels of 90 and 80 for salt and oil mediums respectively, when tested 
in accordance to Annex D  
 
TABLE 1. PERFORMANCE  REQUIREMENTS FOR FACE MASK FOR GENERAL PUBLIC USE  
 
Test Requirement(s)  
  
Decomposable carcinogenic aromatic amine 
dyes   Shall not be present  
Filter Efficiency levels: (%)  
Salt medium                                                                                   90 
Oil medium                                                                                     80  
Breathability - Differential pressure  (Pa/cm2)    ≤ 29.4 
Breaking strength of mask band at the joint  ≤20 
Microbial cleanliness (bioburden)(cfu/g)  
Coliforms  Nil 
Pathogenic purulent bacteria  Nil 
Total fungal colonies /(CFU/g)  ≤ 100  
Total bacterial colonies /(CFU/g)  ≤ 200  
Ethylene oxide residues (µg/g)  ≤10 
 
 
4.5  Microbial cleanliness (Bioburden)  
When tested according to EN ISO  11737 -1 the bioburden of the medical mask shall be  as shown in 
Table 1.  
 
4.7  Dimensions  
Dimensions and design for face masks for general public use shall be 17.7 X  9.6 length  by width  (cm) 
for adults, and 15 X 8.9 (cm) length by width for children  
 
Note.  Any other size shall be as agreed between purchaser and manufacturer.  
  
5  Labelling and information to be supplied  
The following information shall be supplied in addition:  
a) number of this Kenya  Standard;  
b) Trade Mark of the mask . 
c) Name and physical address of manufacturer  
d) Width in centimetres and length in metres.  
e) The word ‘Sterilized’, if sterile.                                                                                                                                                DKS 2924:2020  
 
© KEBS 2020 – All rights reserved                                                                                  9 f) Mass of package in kilograms and grams.  
 
 
 
 
 
 
 
6.           PACKING  
 
6.1        Face masks  shall be individually packed in paper cartons or any other suitable packages  such as 
cellophane or plastic. The packet shall be well closed on both sides and stuck so as to avoid infiltration of any 
foreign matter into the masks . 
 
 
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ANNEX   A  
(informative)  
Information for users  
 
When breathing, speaking, coughing, sneezing etc., one releases smaller or larger amounts of droplets of  
secretions from the mucous membranes in the mouth and nose. The majority of the nuclei are between  
0,5 μm and 12 μm in diameter and especially t he larger droplets can contain micro -organisms from the source 
site. Nuclei can subsequently spread through the air to a susceptible site such as mouth, eyes and nose or 
sterile equipment.  
 
The face masks intended to be used in operating rooms and health c are settings with similar  
requirements  are designed to protect the entire working environment. This standard, however, describes face 
masks with associated protection levels. As a minimum, face masks for general public use should protect the 
general public  in order to reduce the risk of the spread of infections, particularly in epidemic or pandemic 
situations, like the Covid -19. 
 
If the intended use of the mask is to protect the wearer against infective agents (bacteria, viruses or fungi), the 
use of a resp irator device should be considered. Performance requirements for respirators are the scope of 
EN 149.  
The level of efficiency offered by a mask depends on a number of factors such as the filtration efficiency,  
quality of the material and the fit of the mas k on the wearer’s face. Different designs are suited for different  
applications and the careful choice of mask is therefore important in order to achieve the desired result.  
 
The filtration capacity of mask materials can vary depending on the filter media.  The fit of masks varies  
considerably from those which are held in place by ear loops fastened behind the wearer’s ears to those with  
tie bands around the head and a nose clamp that can be shaped to the wearer’s nose. The effect of a very  
good or less good  fit can be tested in vivo whereas the filtration efficiency may be reproducibly tested in vitro.  
The considerable variations in results when masks are tested in vivo results in the need for large groups of  
test subjects and observations. It is thus usual to characterize mask performance using in vitro tests of the  
material from which the mask is made. It is, however, important to consider the fit of the mask carefully when  
a mask for a certain application is chosen. Users should request such information fr om their suppliers.  
 
A further factor to be considered is the capacity of the mask to absorb moisture from the exhaled air and  
thereby to maintain its performance over a longer period of time. The more advanced designs easily maintain 
their performance through longer periods.  
 
The contamination risk resulting from hand contact with a used mask means that it is essential that the mask  
is taken off and disposed of when no longer worn over nose and mouth. When there is a further need for  
protection then a n ew mask should be put on. Touching a used face mask or putting on a new one should  
always be followed by a full hand disinfection procedure and a used mask should always be disposed of when 
no longer needed or between two procedures.  
 
In summary, to use an  appropriate mask is an effective means to protect the working environment from droplet 
contamination from nose and throat during public discourse. Masks with very different performance are, 
however, available. Therefore,  such factors as infection risk and  mask fit should be carefully considered when 
choosing a mask.  
 
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© KEBS 2020 – All rights reserved                                                                                  11  
Annex B  
Cleaning and disinfecting  
(Normative)  
B.1 General  
 
B.1.1 A total of 2 particle filtering half masks shall be tested: both as received.  
 
B.1.2 All tests shall be carried out by two test subjects at ambient temperature and humidity shall be 
recorded.  
 
B.1.3 Prior to the test there shall be an examination to assure that the particle filtering half mask is in good 
working condition and that it can be used without hazard.  
 
B.1.4 Examinat ion shall be done in accordance with clause B.1.3. 
 
B.1.5 For the test, persons shall be selected who are familiar with using such or similar equipment.  
 
B.1.6 During the tests the face mask shall be subjectively assessed by the wearer and after the test, 
comments on the following shall be recorded:  
 
a) security of fastenings  
c) field vision  
d) any other comments reported by the wearer on request.  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
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© KEBS 2020 – All rights reserved    12 
 Annex C  
(normative)  
Method for determination of breathability (differential pressure)  
 
C.1  Principle  
A device which measures the differential pressure required to draw air through a measured surface area at a  
constant air flow rate is used to measure the air exch ange pressure of the medical face mask material, as 
shown in Figure C.1. Water -filled manometers (M1 and M2) are used to measure the differential pressure. A  
flow meter is used for measurement of the airflow. An electric vacuum pump draws air through the a pparatus  
and a needle valve is used to adjust the airflow rate.  
 
 
 
 
 
 
Key 
1 drive mechanism      8 microbial sampler  
2 bacterial suspension      9 outlet to sink  
3 nebulizer       10 condenser  
4 filter        11 cold water inlet  
5 aerosol chamber      12 calibrated flow meter  
6 high pressure air source     13 compressor (vacuum pump)  
7 test material  
 
Figure C.1 — BFE test apparatus  
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© KEBS 2020 – All rights reserved                                                                                  13  
 
 
 
C.2 Apparatus  
C.2.1 Flow meter, capable of measuring an airflow of 8 l/min  
C.2.2 Manometers, M1 and M2 or differential manometer  
C.2.3 Electric vacuum pump  
C.2.4 Valve  
 
C.3 Test specimens  
Test specimens are complete masks or shall be cut from masks. Each specimen shall be able to provide 5  
different circular test areas of 2,5 cm in diameter. If one specimen cannot provide 5 test areas of 2,5 cm in  
diameter, the number of test areas retrieved should be representative for the entire mask. The number of  
specimens that shall be tested is minimum 5, but can be greater and shall be increased if necessary to allow  
for an AQL of 4 %. All specimens tested shall be taken from areas representative from the mask to  
incorporate all/any variation in construction.  
 
Each test specimen shall be conditioned at (21 ± 5) °C and (85 ± 5) % relative humidity for the time required 
to bring them in to equilibrium with atmosphere prior to testing.  
 
C.4 Procedure  
C.4.1 The test specimen is placed across the 2,5 cm diameter orifice (total area 4,9 cm 2) and clamped into  
place so as to minimize  air leaks and that the tested area of the specimen will be in  line and across the flow of 
air. 
 
C.4.2 The pump is started and the flow of air adjusted to 8 l/min.  
 
C.4.3 The manometers M1 and M2 are read and recorded.  
 
C.4.4 The procedure described in steps C.4.1 through C.4.3 is carried out on 5 (or appropriate number of)  
different areas of the mask and the readings averaged.  
 
C.5 Calculation of differential pressure  
For each test specimen calculate the differential pressure ΔP as follows:  
ΔP = (Xm1 – Xm2)/4,9 
where  
Xm1 is pressure in Pa, manometer M1, mean of 5 test areas, low pressure side of the material;  
Xm2 is pressure in Pa, manometer M2, mean of 5 test areas, high pressure side of the material;  
4,9 is the cm2 area of the test material;  
ΔP is the differential pressure per cm2 of test material expressed in Pa . 
 
C.6 Test report  
The following information shall be given in the test report:  
a) number and date of this Publicly Available Standard;  
b) lot number or batch code of the masks tested;  
c) flow rate during testing;  
d) differential pressure for each test specimen.   
 
 
 
 
 
 
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Annex D 
(normative)  
Test for filter efficiency  
 
 
D.1 Principle  
Aerosol particles of a certain concentration and particle size distribution are generated by the aerosol 
generator, passed through the mask cover at a predetermined gas flow rate. An appropriate particle detector 
shall be used to detect the particle size through the mask body. The percentage of particle matter reduction 
before and after the aerosol passed through the body of mask is used to evaluate the filtering efficiency of  the 
mask body.  
 
D.2 Samples and pre -treatment  
D.2.1  Sixteen samples are divided into two groups of eight each ; One group to be tested in the oil medium 
while the other is to be tested in salt medium.  
 
D.2.2  Five samples are untreated, while the other thre e samples are pre -treated as described in D.3. 
 
D.3 Pre-treatment by temperature and humidity  
D.3.1.1  Pre-treatment equipment  
a) Test Chamber for humidity tests  
b) Test Chamber for high/low temperatures  
 
D.4 Method  
Take the samples from original package and pre -treat as follows;  
a) Keep requisite test samples at 38±2.5 ⁰C and 85±5 relative humidity for 24±1 hrs  
b) Keep designated samples at 70±3 ⁰C dry environment for 24±1 hrs  
Keep designated samples in 30±3 ⁰C for 24±1 hrs . 
Before undertaking any step, ensure that the temperatures of all samples are conditioned at room 
temperatures. Pre -treated samples shall be placed in closed containers/chambers and tested within 10 hours.  
 
D.5 Equipment  
D5.1 Filter efficiency test system for NaCl particles meeting the  following requirements;  
a) The concentration of NaCl particles are less than 30 mg/m3. The count median diameter (CMD) is 
(0.075±0.020) µm, and the geometric standard deviation of particle size distribution size is less than 1.86.  
b) b) The detected dynam ic range of particles is 0.001~100 mg/m3, and the accuracy is 1%.  
c) The detected flow range is 30 ~ 100L/min, and the accuracy is 2%.  
d) The testing range of Filter efficiency is 0~99.999%.  
e) There shall be a neutralized device for neutralizing the charge of particles.  
 
D. 5.2 Filter efficiency testing system for oil particles  
The requirements of Filter efficiency test system for oily particles are as following:  
a) Test medium is dioctyl sebacate (DEHS) or other applicable oily particles, such as par affin oil. The  
particle concentration is less than 30 mg/m3, and the count median diameter (CMD) is (0.185 ±0.020) μm. 
The geometric standard deviation of particle size distribution is less than 1.60.  
b) The detected dynamic range of particles is 0.001~100 mg/m3, and the accuracy is 1%.  
c) The detected flow range is 30 ~ 100L/min, and the accuracy is 2%.  
d) The test range of Filter efficiency is 0~99.999%.  
 
D. 6 Test conditions  
The test ambient temperature is (25 ±5) ℃ and the relative humidity is (30 ±10) %.  
 
 
 
 
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A. 7 Test process  
a) Test air flowing is (85 ±4) L/min (the air flowing should be divided equally if adopt multiple filtering  
element, such as dual filter element. The test flow of each filter element should be (42.5 ±2) L/min; if the  
multiple filter element may be used alone, the test shall be applied as single filter element).  
b) Adjust Filter efficiency test system and the relevant parameters into test condition.  
c) Fix the main body of the mask or filter element to the detection device airtight.  
d) Record sample Filter efficiency after test start and the sampling frequency is no less than 1 time/ min.  
The test shall be continued until particles on mask loaded to 30 mg.  
 
A. 8 Data processing  
Take the minimum value in the course of the entire test as the Filter efficiency for the batch of test  
samples. The value keeps a decimal.