KENYA STANDARD         DKS 94:2016  
 
 . 
 
 
 
 
  
 
 
 
Preservation of timber —Specification 
 
 
 
 
 
 
 
 
 
 
 
 
 
  
 
  
 
©KEBS 2016        4
th Edition 2016  
 
 
 
  
 
 
 
   
 
  
 
 KS 94:2016           
 
ii        © KEBS 2016— All rights reserved TECHNICAL COMMITTEE REPRESENTATION 
 
The following organizations were represented in the Technical Committee: 
 
1. Marlow Link Timber  2. KAKUZI 
3. HIGHCHEM  
4. Millennium Trading House Limited 5. National Environmental Management Authority (NEMA) 
6. Kenya Forestry Research Institute (KEFRI) 
7. Pest Control Products Board (PCPB) 
8. University of Eldoret 9. PEMAK 
10. Alogo Enterprises 
11. COSTEK ALMA 12.        Kenya Power   
13. Kenya Wood Preservers Association 
14. Muringa holdings 15 Kenya Bureau 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, 2016 
  Copyright. Users are reminded that by virtue of Section 25 of the Copyright Act, Cap. 12 of 2001  of the Laws of Kenya, copyrig ht 
subsists in all Kenya Standards and except as 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 w riting 
from the Managing Director. 
 
  
 
     
 
 
 
 
 
  
 
 KS 94:2016   
 © KEBS 2016 — All rights reserved           iii  
 
 
           
 
 
 
  
 
 
  
 
 
 
 
Preservation of timber —Specification 
 
 
 
 
 
 
  
 
 
KENYA BUREAU OF STANDARDS (KEBS) 
 
Head Office:  P.O. Box 54974, Nairobi-00200, Tel.: (+254  020) 6005490, 6002350, Fax: (+254 020)  6004031 
E-Mail: info@kebs.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 Te l.: (+254 057) 23549, 22396       Tel.: (+254 051)  210553, 210555 
Fax: (+254  041) 229448   Fax: (+254 057) 21814
        
 
 
  
 
 
 
 
 
 
 
 
 KS 94:2016           
 
iv        © KEBS 2016— All rights reserved  
 Foreword 
 
This Kenya Standard was prepared by the Timber and Timber products Technical Committee and under the guidance of the Standards Projects Committee, and it is in accordance with the procedures of the Bureau. 
 
It is general  experience that the satisfactory performance of a wood preservative depends not only on the efficiency of the preservative itself but also on the method of its application to the timber, the treatability of 
the timber and the environment in which the treated timber is to be used. It is hoped that this standard will 
create awareness and a better understanding of the many factors involved in timber preservation. 
 This standard specifies the chemical compositions of the most commonly used locally available 
preservatives, the most common methods of applicati on and average retention of preservative levels for 
various species of timber in a variety of environmental conditions.  
The standard is as comprehensive as practically po ssible. It will be revised to include additional 
preservatives and preservation processes after they become established in Kenya.  
In the preparation of this standard, reference was made to the following publication: 
  As 1604 -1980  Preservative treatment for sawn timber, veneer and plywood. 
 
 BS 1282 Guide to the choice, use and application of wood preservatives.  
 BS 4072 Specification for wood preservation by means of water-borne   
   copper/chrome/arsenic compositions.  
Acknowledgement is hereby made for the assistance derived from these sources.  
 
Acknowledgement is hereby made for the assistance derived from the above sourcesKS 94:2016 
© KEBS 2016 – All rights reserved 1 
Preservation of timber — Specification  
 
1. Scope  
 
This Standard specifies requirements for preservative  treatment of timbers. The preservatives, safe 
methods of application and chemical balance avera ge retention levels have all been specified with the 
object of achieving long service life.  
 
2. Applicatio n 
In order to comply with this standard, treated ti mber shall satisfy the requirements for preservative, 
preservative penetration and average retention levels specified herein. 
 
3. Definitions 
For the purpose of this standard the definitions given in KS 02-93 shall apply, except where otherwise 
defined as follows: 
 
1.1  
charge retention   
the net absorption of preservative by wood as calc ulated from the charge sheet excluding the solution 
leakage and dripping losses.  
  
1.2  
retention 
the net absorption of preservative by the wood 
 
1.3  
retention zone 
the area of the cross section which contai ns a specific amount of preservative.  
 
1.4  
sample 
the timber chosen, on which process quality control measurements are made for the purpose of checking 
conformance with this standard   
1.5   
treated timber   
timber purporting to comply with the requirements of this standard 
 
4. Preservatives  
 
4.1. copper — chrome — arsenic (CCA) compounds soluble in water 
 
4.1.1. These preservatives are water soluble mixture of chrome, copper and arsenic salts of oxides of 
these metals.  They are supplied ready-mixed in liquid form. 
 4.1.2. Specification for CCA 
 
i) The treatment solution shall be of concentrati on containing not less than 3% of concentrate"
 of 
salt or its equivalent oxide per volume of solution and as per the data sheet. 
 
                                                      
 Glossary of terms used in timber  
2        © KEBS 2016— All rights reserved ii) The CCA preservative shall be in a form which shall dissolve in water to give a solution containing 
the active elements copper, chromium and ars enic in the proportions specified in Table 1.  
 
iii) On dissolving in water and stirring, bu t keeping the solution temperature below 400C, insoluble 
matter shall not exceed 0.5 per cent of the solid preservative formulation. 
  
 Table 1ـProportions of active elements in CCA Preservative 
 
ELEMENT Proportion, per cent 
Minimum  Maximum 
 
Copper  
 
Chromium 
 Arsenic  
30 
 
35 
 18  
40 
 
50 
 32 
   
 
ELEMENT  Proportion, per cent 
Minimum  Nominal  Maximum 
 
Copper oxide    Chromium trioxide  Arsenic pentoxide   
10.0  26.3  17.7  
11  28  20  
12.4  29.8  22.4 
 
 
4.1.3. The desired oxides formulations can be obtai ned from various water soluble compounds of 
chromium, copper, and arsenic.  
4.1.4. A three per cent aqueous solution of corre ctly formulated preservative shall have a Hp of 2.0 to 
2? 
 Note: Timber treated with CCA preservative must be retained at  the treatment plant for 72 hours to allow the preservative to 
become fixed in the timber. 
 
4.2. Coal tar creosote or creosote solution 
 
4.2.1. Creosote — A coal tar distillate shall have the following properties:  
 
i). Density — specific gravity at 380C shall not be less than 1.003. 
 
ii).  Liquidity — the creosote shall become completely liquid on being slowly warmed to 380C with 
stirring.  On cooling it shall remain liquid after standing for two hours at 320C. 
 
iii). Water content — the creosote shall contain not more than 1.5 per cent by volume water. 
 
iv). Toluene insoluble matter — The creosote shall yield not more than 0.5 per cent by mass residue 
insoluble in toluene. 
 
v). Distillation range — On distillation of water-free and previously liquefied creosote the distillates 
shall be within limits specified in Table 2. 
 KS 94:2016 
© KEBS 2016 – All rights reserved 34.2.2. Creosote oil solution  — this shall be a blend of creosote as specified in Clause 4.2.1 and a 
heavy petroleum oil.  Other additives may be included provided that the resulting preservative solution 
shall contain by mass not less than 60 per cent creosote. 
Table 2ـDistillation limits of coal tar creosote 
 
Temperature 0C Cumulative distillate, per cent mass 
Minimum maximum 
 
205 
 230 
 
315 
 
355  
- 
 - 
 
40 
 
65  
5 
 30 
 
78 
 
- 
 
Copper  azoles  
The chemical composition of the new copper ba sed environmentally friendly wood preservatives are 
complex formulations of either  
 Copper azole 
 Ammoniacal copper quaternary (ACQ), and their generics, in liquor formulations  
 
These in liquor formulations shall comply with regist ration regulations of the Pest Control Products Board 
(PCPB) of Kenya and specific data in the materi al safety data sheet/labels of the particular(s). 
 
Any changes in the chemical formulation of the regist ered wood preservative shall be ratified by the PCPB 
and must be in consistent with the Environmental  Management Coordination Act CAP 387 of Kenya and 
subsequent legislations. 
 4.4  ACQ 
 
The ACQ registered by PCPB (PER MAWOOD ACQ 1900 Reg. No. PCPB 9CR) 1101) has the following 
details which can be found in the PCPB Li st of Registered Products and the label. 
i. Composition of product: Basic Copper Ca rbonate 17.3% + Alkyldimethyl benzylammonium 
Chloride 48% 
ii. Application rates :  applied at concentration of 4%  
iii. Retention rates:  At the recommended concentration of 4% , the retention levels (kg/M
3) was 
determined to be:  Eucalyptus heart wood 3.4 and sap wood 6.6 
iv. Application process: The wood sample is tr eated in a vacuum/ pressure treatment plant. 
v. Test Method/ Determination method:    
  
 
  
4        © KEBS 2016— All rights reserved  
5. Preservation processes 
 
In this standard four processes are specified, namel y vacuum pressure process, diffusion process, hot 
and cold open tank process and sap displacement process. 
 
5.1. General   
It is desirable that all timber should be cut and dri ed prior to treatment; where this is not possible cut 
surface shall be liberally brushed with preservative solu tion.  The aim is to maintain an outer envelope of 
treated timber.  
 
5.2. Vacuum pressure impregnated method  
This method is suitable for treatment of timber with all types of preservative solutions.  When properly 
controlled the method allows mot? reliable and consist ent results.  This method is described in Appendix 
A (i). 
 
5.2.1. In general, control shall be exercised over the following: 
 
(i) Moisture content — The average moisture content shall not be more than 20 per cent for softwood 
and 25 per cent for hardwood. 
(ii) The concentration, volume and temperature of preservative solution 
(iii) The levels and duration of the vacuum and pressure cycles. 
(iv) Impregnation solution temperature — The treatment solution shall be 85ºC to 100 ºC at the time of 
impregnation in the case of creosote preservative s. The temperature of CCA solutions shall not be 
higher than 40ºC. 
 
5.3. Diffusion process 
This process is suitable for use with boron salts. The wood to be preserved by diffusion shall be green, straight off the saw. The process is not suitable for preserving wood milled from dead trees, since this is 
generally too dry for diffusion to occur; conversely, timber which is wet with rain water should not be 
preserved by diffusion as the rain water can dilute the chemicals too much.  The process is described In 
Annex A (ii). 
 
5.4. Hot and cold open tank process  
This process is suitable for creosote. It is not for us e with waterborne preservatives.  It does not allow for 
close control directly as in the ca se with pressure impregnation met hods, but the treatment is adequate, 
sometimes even being excessive.  The process is described in Annex A (iii). 
 
5.5. SAP Displacement process  
This is a process of treating small round timbers such as fence posts with CCA preservatives.  The process is described in Annex A (IV).  
Note: In general, for methods in clauses 5.2 to 5.5 control must  be exercised over the volume and species of the charge.   Only  
timber of one species shall be included in a charge, otherwise if  a charge is made up of different types of timber, the treatme nt shall 
be controlled so as to ensure adequate treatment of the species most resistant to treatment. 
 
5.6. Preparation of timber for pre-treatment 
 
5.6.1. Surface Condition   
The surface of the wood shall be free from inner and outer bark, dirt or any other surface covering. 
 
5.6.2. Decay and Insect Damage The wood shall be free from fungal or insect attack , other than sap stain and negligible pinhole bores 
subject to acceptance by the purchaser.  
 5.6.3. Prefabrication   KS 94:2016 
© KEBS 2016 – All rights reserved 5As far as possible all manufacturing involving wood cutting, such as cross-cutting and rebating, shall be 
carried out before preservation treatment. 
 
5.7. Environmental and Occupational Health  
The treatment plant shall meet all the relevant requirements as provided for in the Environmental 
Management and Co-ordination Act, 1999 and its subsequ ent regulations. The operators of such plants 
shall be mandated to consult the environment agency from  time to time for purposes of advice, guidance 
and necessary authorization.  
5.7.1. Environmental Health  
The treatment plant shall be designed to prevent c ontamination of water supp lies, drainage systems, 
rivers, lakes and streams; discharge into these shall not be allowed.  Leaks and spillages shall be 
contained by an effective bund wall around the treatment  plant, and these solutions, plus drippings from 
treated wood, shall be run off into a suitable sump and returned, if suitable, into the working solution. 
 
All pesticide containers and pesticide waste such as contaminated tree barks & sludge should be 
disposed by a pesticide waste incinerator licensed by relevant government agencies (NEMA and PCPB). 
5.7.2. Personal Health Precautions  
 When handling preservatives and freshly treated tim ber avoid skin contact and avoid inhalation of dust 
and vapours.  Wear waterproof aprons/overalls, PVC  gloves or gauntlets.  Wear breathing masks when 
handling powders and eye protection goggles when handling solutions. 
 Washing facilities with running water and soap and also  skin barrier creams shall be available at treatment 
plants. 
 After handling the chemicals, and before eating food, wash hands and face with soap and clean water.  
Smoking or eating shall not be permitted whilst handling preservatives. 
  
6. Preservative rete ntion and penetration 
 
The degree of preservation is expressed in two ways; retention and penetration.  
6.1. Retention 
 6.1.1. Retention is expressed as the we ight of preservative chemical contained in one cubic metre of 
treatable wood.  Retention gives no indication of dist ribution of the chemicals in the wood; it may be 
uniformly distributed across the sections or  contained in a thin skin on the surface. 
 
6.1.2. Treated timber shall contain the suggested minimu m amounts of preservative as required in Table 
4, either as the certified average of a charge or on analysis of sufficient samples. 
 
6.1.3. Analysis of CCA preservative treatment shall be based on chemical or physical analysis as per 
Appendix D.  
6.1.4. Analysis of oil preservative treatment shall be ba sed on extraction of moisture-free preservative 
solution from specimens of accurately measured volume (see clause C2).  KS 94:2016 
© KEBS 2016 – All rights reserved 1Table 4. Recommended average retention levels for common applications of impregnated timbe r 
 
 
Hazard 
Class Service Conditions (Exposure 
class) Timber Application End Use CCA formulations Av. 
Net Retention (kg/m3) Creosote or 
creosote oil 
solution Av. Net  
Retention (kg/m3 ) Min. Preservative 
penetration 
(assay zone) 
(mm) 
H1 Internal Timber used under a roof, not in 
contact with the ground, and will not be exposed to leaching and weathering Sawn Timber, Mouldings, 
ceilings, floorboards, joinery Not recommended Not recommended  
H2 Interior timbers not in contact with 
the ground, not exposed to the 
weather and not in a dry-wood termites area Interior timbers used in roofs, interior 
joinery timbers etc. Poles : Building Structures, roof, 
trusses 
Sawn Timber : Laminated beams, 
roof trusses, structural timber, 
ceiling boards, flooring, panelling, 
doors cupboards, skirting, window 
frames, plywood, slabbed poles, cylindrical rail General purpose poles, machined 
poles for log homes 6.0 80.0 Complete Sapwood 
H3 Exterior above ground Timber not in contact with the ground 
but exposed to leaching and weathering Poles : Cross-arms and spacers 
 
Landscaping structures, play-ground structures, building, 
fencing rails, pergolas, carports, 
vine trellises Round droppers Spacer blocks 
 Sawn Timber (and specified 
round timber):  Balustrades, 
fencing bearers and slats, out-
door decking and beams, garden 
furniture, laminated beams, weather boards, steps, cladding, 
stairs, gates, Fascia boards 
plywood, sawn droppers, slabbed poles, cylindrical rails  
General purpose poles, machined 
poles for log homes Lath  12.0 
   
8.0 
   
 
   
 
8.0 100.0 
   
80.0 
   
 
   
 
80.0 Complete Sapwood 
H4 Ground Contact Timber in direct contact with the 
ground Poles : Distribution 
 
Telephone & Street Light 
 Agricultural poles; landscaping 16.0 
 
16.0 
  115.0 
 
115.0 
  Complete Sapwood 
 
 
   
2        © KEBS 2016— All rights reserved structures, playground, building, 
fencing, pergolas, carports, flower boxes, vine & orchard trellises 
Posts (guard-rail) 
Piling; agricultural poles for livestock pens  
Sawn Timber: Sawn rectangular 
posts, landscaping structures, 
playground structures, building, fencing, pergolas, carports, flower 
boxes, decking, bridges 
Rail bearers 12.0 
  
 
   
 
   
 
 12.0 100.0 
  
 
   
 
   
 
 100.0  
  
 
   
 
   
 
  
Complete Sapwood 
H5 Fresh Water Timber in constant or periodic  with 
fresh water or heavy wet soils Poles : agricultural poles, poles 
under flood irrigation, bridges, piling, groynes, walkways, slipways, jetties, agricultural poles for livestock pens/ retaining walls  
 Sawn Timber : Piling, groynes, 
jetties, walkways, retaining walls, 
culverts, flood gates, drains 
Industrial cooling towers 16.0 
 
   
 
 16.0 130.0 
 
   
 
 130.0 Complete Sapwood 
 
   
 
 Complete Sapwood 
H6 Marine   Timber in constant or periodic contact 
with estuarine or sea water and subject to marine borer attack  Poles : piling, retaining walls. 
Slipways, groynes, jetties, 
walkways 
 Sawn Timber : piling, retaining 
walls. Slipways, groynes, jetties, 
walkways 24.0 
  
 
24.0 200.0 
  
 
200.0 Complete Sapwood 
 
 
  
   KS 94:2013  
  
 
 
 Transmission poles: The minimum target retention in the assay zone for H4 timber treated to an average of 16KG/m3.   Building and fencing material  (light poles) : The minimum target retention in the assay zone for H4 timber treated to an avera ge of 
12KG/m3  total timber  volume. Shall not be less than 24kg/m3 in the (assay) sapwood zone.  
 
Notes:  1. At the time of producing this standard the drywood termite areas those areas which are within 50 kilometres of the coasts of  the 
Indian Ocean and Lake Victoria 
 2. For the higher hazard classes it is important to use a treatable timber that can be penetrated to a sufficient depth so as t o provide a 
complete envelope of impregnated timber. For example, gum poles have treatable sapwood.  So, when used in the  round form 
the treated sapwood provides the complete envelope of impregnated timber. 
 3. Cypress has moderately treatable sapwood but heartwood that is resistant to treatment; heartwood penetration is  unlikely to  
exceed 6 mm to 10 mm and as such is not a suitable timber for high hazard situations.  4. Of the less common species of timber some are more resistant to treatment than others. Specific advice from the Forestry 
Department should be sought in individual cases. 
 
 
6.2. Penetration 
 
6.2.1. Penetration is the depth of wood from the surface which has been impregnated with preservative 
 6.2.2. Penetration shall be measured on a cross-section cut at least 50cm from the end of the timber or in 
the case of treated poles or baulks on a boring made right through the section with a hollow core 
increment borer. Ots? determination is described in Appendix E. 
  6.2.3. Requirements   
 A complete envelope of treated timber and, complete sapwood penetration. 
 
Note: The sapwood of most species is perishable but usually treatable and complete penetration is desirable, especially for hig h hazard 
situations. 
 
7. Sampling  
 
7.1. Preservatives 
 
7.1.1. The sampling shall be made on batches delivered to treatment plants and a composite sample of 
about one litre or one kilogram is generally adequate. 
 
The same safety precautions necessary in treating timber shall be taken while sampling and handling the sample.  Gloves of PVC, or preferably of polychloroprene, goggles or a face shield, and an apron need to be 
worn while handling powder preservatives (see clause 5.6). 
 7.1.2. Solid Preservatives  
 A special instrument known as a “thief sampler” is needed to take several samples from each container.  
The samples shall then be thoroughly mixed by heaping into cores followed by flattening several times, quartering the heaps, and repeating the mixing and subdivision to leave a sample of approximate size of 
analysis.  Great care is necessary to avoid contamination or changes of moisture content during the 
sampling process.  7.1.3. Paste or liquid preservative 
 A sampling container shall be used to draw samples after thorough mechanical mixing of the preservative to 
as much homogeneity as possible.  From each container samples are drawn from near the top, mid-depth and base of the container.  These are then th oroughly mixed and subsampled as necessary. 
 
Oil preservatives are similarly sampled and where solid deposits form at low temperature the oil shall be warmed to complete liquidit y before taking samples. 
 
7.1.4. Solution  The container shall be clean and have a tight sealing lid, about 10 per cent air space should be left.  About 10 g is needed for a physical analysis or 300 ml for a chemical analysis.   KS 94:2013            
  
 
7.2. Treated timber 
 
7.2.1  Lengths of timber shall always be selected by random sampling from consignments or charges.  Test 
samples for preservative analysis shall be obtained from not closer than 500 mm from the end grain surface, 
and not within 3 days of treatment.  
7.2.2  Generally the most appropriate test specimens shall be complete cross-sections for converted timber 
and increment cores for round poles and baulks.  The increment cores shall pass right through the pole or fitting plugs of treated timber so as to make the timber fit for use.  
Test specimens shall invariably consist of sound wood.  Wood with, or close to, growth defects such as knots 
and mechanical defects should be avoided.  
8. Marking  
 
8.1. Timber preserved by pressure impregnation or diffusion process shall be legibly and indelibly 
marked with the following particulars: 
 
i). The name of the preservation plant 
 
ii). The hazard class 
 
iii). The year of treatment 
 
iv). The number of this standard. 
 
9. Certificate of treatment 
 
9.1. The purchaser of pressure impregnated timber shall be supplied with a certificate of treatment and 
charge sheet details.  
9.2. Treatment firms shall retain for a period of a t least 5 years records of treatment and results of any 
tests made to determine penetration and retention. 
                     KS 94:2013  
 
 
. 
 
© KEBS 2013 — All rights reserved         
     3
 Annex A 
 
(i) Vacuum Pressure process 
 
A(i) 1. General   
 
This method is usually used with CCA salts or creosote oil solutions.  
A (i) 2. Apparatus 
 The essential equipment shall be an airtight pressure cylinder in which timber completely immersed in 
solution shall be subjected to hydraulic pressure to mechanically force the solution into the wood cells.  
Associated equipment shall consist of pumps, preservative mixing and storage tanks, piping and various gauges. Where the preservative solution is a heavy oi l –auxiliary, heating equipment shall form an integral 
part of the preservation plant. 
 A (i) 3  Procedure  
 
A (i) 3.1 Inspect timber to be treated, for suitability of species or defects, for example: 
(a) Decay (b) Insect infestation  
(c) High moisture content 
 A (i) 3.2  Timber dried to below 20 per cent moisture content for softwoods and to below 25 per cent moisture 
content for hardwoods and prepared for a treatment charge shall be placed in the pressure cylinder which 
shall then be sealed airtight.  There are variations  of the impregnation proces s which follow as detailed 
below: 
 
A (i) 3.2.1  Full cell (or Bethell) Process  — Before admission of the treatment solution into the pressure 
cylinder, a vacuum of more than 500 mm mercury shall be applied for a period of about 30 minutes.  With 
vacuum still on, still on, the solution, at appropriate temp erature, shall be added to f ill the cylinder completely.  
Then a maximum pressure of up to 1.5 MPa, depending on the type of timber, shall be applied for a period of 1 hour to 6 hours until it is seen that the required amount of preservative has been absorbed.  The cylinder 
shall then be emptied of the solution and a final vacuum similar to the initial vacuum may be applied.  The 
initial vacuum empties all the caviti es of air to leave space for the treatment solution on application of 
pressure.  The final vacuum serves to minimize su bsequent bleeding and leave the wood surface dry for 
clean handling. 
 A (i) 3.2.2  Empty Cell Process  — with timbers which readily absorb preservative solutions and to avoid too 
much retention the initial vacuum shall be omitted.   The cylinder shall be filled with the treatment solution 
while at atmospheric pressure (Lowry process). A small initial pressure is sometimes applied in the cylinder 
and filling with solution takes place at this pressure (Rueping process).  After filling the cylinder details of 
treatment which shall be followed are the same as in the full cell process.  
 
The pressure period allows the interior  of wood to be filled with the treatm ent solution.  When  the pressure is 
released, the resulting expansion of the compressed air in the cell cavities forces out some of the absorbed 
solution.   More solution is recovered on application of a final vacuum. 
 By adjusting the amount and duration of pressure, the quantity of solution absorbed by the timber in the 
charge can directly be controlled to the desired levels. 
 
(ii) Diffusion process  
 
A (ii) 1  General  
 
This method is usually used with boron salts; it is not suitable for CCA, creosote oil solutions. 
 A (ii) 2  Apparatus    KS 94:2013            
  
Mixing tank, circulating pump, fine mesh hard strainer, pipes, reinforced plastic  covers, etc. 
 
A (ii) 3. Procedure  
Estimate the volume of solution required for the day’s ru n.  Fill the mix tank up with clean water to 85 per 
cent of the solution.  Calculate the weight of salt requ ired and the concentration.  Add the salt to the mix tank, 
stirring thoroughly and running the circulating pump, until all salt is dissolved.Top up with water to the 
required volume.  The timber to be treated shall be cut the same day from green logs free from decay or blue 
stain.  It shall not be wet with rain.  Dip or spray the timber, maintaining the temperature.  At the end of the day’s operations clean out all saw dust with a fine mesh hard strainer and dilute the remaining solution to 
about 50 per cent of the average working volume. 
 
The timber shall be completely submerged or sprayed.   Immediately after dipping or spraying, the timber 
shall be built into square ended block stacks 100 mm clear of smooth level ground.  Every effort should be 
made to shake free as little as possible of the solution off the timber. 
 When the stacks are completed they shall be covered on top sides and ends with tightly fitting impermeable 
cover to exclude all outside air.  Laps in the cover shall be a minimum 0.5 m.  The covers shall extend over 
the ground 0.5 m and shall be firmly held down with weights, stones or timber.  
(iii) Hot and cold open tank process 
 A (iii) 1 General  
 
This method is usually used for creosote oil solution.  
A (iii) 2 Apparatus 
 A strong open tank of any convenient size and shape with provision for heating the treatment solution 
 
A (iii) 3 Procedure 
 Suitable dried timber shall be immersed in the preservative solution which is heated to 90
0C to 1000C and 
maintained at that temperature for a period of about 3 hours to 4 hours.  With the timber still immersed, the 
tank shall be cooled to allow absorption of the solution due to contraction of the residual air in the wood cell cavities. Alternatively the wood is quickly transferred to a tank with cold preservative solution. The 
appropriate duration of heating timber at the maximum treatment temperature and the cooling period of the 
hot bath, or the period of immersion in cold bath, are adjusted to suit the specified penetration and retention.  
  
A (iii) 4 Precaution 
 There exists risk of fire breaking out if the solution spills over the tank. Therefore the solution shall not be 
heated above the specified temperature as there is likelihood of the solu tion frothing and spilling over. For 
the same reason, indirect heating by steam is preferable to direct fire. The tanks shall be kept covered to avoid solution contamination with dust and moisture.  
 
 
(iv) Sap Displacement Process 
 
A (iv) 1.General 
 
A method of treating small timbers such as fence posts with waterborne preservatives. 
 A (iv) 2 Preparation of Posts The posts and droppers shall be barked and placed in the treatment solution 
within 24 hours of felling the tree.  Building posts and fence posts should be treated in the lengths in which 
they are to be sold.  Droppers should be treated in 4 m lengths.  
 
Bamboos should be treated with their leaves and branches left on within 24 hours of cutting.  
 
A (iv) 3. Solution Strength                     KS 94:2013  
 
 
. 
 
© KEBS 2013 — All rights reserved         
     5
  
For most purposes a 6 per cent solution is adequate, but should a larger or a smaller retention than normal 
be required, then, a more concentrated or less concentrated solution can be used.  To make up a 6 per cent 
solution 8 kg of a copper/chrome/arsenic salt are dissol ved in 135 litres of water. (This volume of water is 
suitable for treatment in a 200 litres drum). 
 
A(iv) 4 Treatment Drums should be placed in as hot and sunny a place as possible, preferably where there is a wind.   
Optimum results are obtained where the drying rate is highest.   Posts and bamboos should be placed in the 
drums and left for four to six days whereas droppers can be removed after three days.  Long posts or bamboos required to be rested against some kind of fr ame or support to prevent them overturning the drums.  
 
Wet weather, high humidity or cold weather slow down the treatment so that treatment needs to be adjusted from the 4 days to 6 days average to suit varying conditions.  It is strongly recommended that anyone 
intending to use this treatment should calculate the volumes of a few trial batches and treat them until an 
overall retention of 12 kg/m
3 is obtained so as to give then an idea of the length of treatment required to suit 
the particular conditions.  
 
The posts should be kept for one week treatment before being used to allow the preservative to become fixed in the timber.  It is strongly recommended that after 3 days in the solution, fence posts should be reversed for the last day so as to treat the top of the post better.  If this is done, adequate treatment is 
obtained in 4 days. 
  
Annex B 
Method for determination of preservative penetration 
 
B1 Test Specimens  
 
Penetration is best measured on a freshly prepared end grain surface; alternatively the measurements can be taken on increment cores.  The end grain surface shall be cut at least 500 mm from the end of the treated 
timber because penetration along the grain is easy and good penetration is always achieved near the ends 
of preserved timber.  
 
B2 
Measurement of penetration  
 
B2.1 Oil Preservatives  
The depth of penetration is easily seen on the end grain surface.  If the sample has been recently treated, the saw or the core bores may smudge the oil over unpenetrated parts of the timber.  
B2.2  Waterborne Preservatives   
Sometimes the depth of penetration is not apparent, in which case it is necessary to treat the surface with a chemical indicator which changes colour in the presence of surface is made smooth by planning or 
sandpapering and the chemical indicator applied sparingly, ideally by spray but a rag moistened with the 
chemical indicator is better than wetting the test specimen with indicator.  
B3. 
Measurement of Penetration  
 
B2.1 Oil preservatives  The depth of penetration is easily seen on end grain surface.  If the sample has been recently treated, the 
saw or the core bores may smudge the oil over unpenetrated parts of the timber. 
 
B2 Measurement of penetration  
 
B2.1 Oil Preservatives 
Sometimes the depth of penetration is not apparent, in which case it is necessary to treat the surface with a 
chemical indicator which changes colour in the presence of the preservative.  Best results are achieved 
when the end grain surface is made smooth by planning or sandpapering and the chemical indicator applied   KS 94:2013            
 sparingly, ideally by spray but a rag moistened with the chemical indicator is better than wetting the test 
specimen with indicator. 
 
B3 Copper  
 
B3.1 Chrome Azurol S Test 
 
Reagent: 
A solution containing 0.5 per cent chromo azurol S dye and 5 per cent sodium acetate in distilled water. 
 Application: 
Light spray gives a strong royal blue colour in wood with copper, persistent for several weeks. Untreated 
wood becomes orange coloured  
B3.2  
Rubeanic Acid Test  
 
Reagents: A 5 per cent ammonium solution made by diluting 1 part ammonia (0.880) with 6 parts water by volume – 
solution A. 
 A 0.5 per rubeanic acid made by dissolving 0.5 g ru beanic acid (dithio-oxamide) in 100 ml ethanol or 
methylated spirit – Solution B 
 Application: 
Spray with solution A followed by solution B produces a royal blue colour in wood containing arsenic. 
  
B5 
Pentachlorophenol in oil solution   
 
B5.1 Cuprin Acetate Test  
 
Reagent:  Cupric acetate and 0.5 g wetting agent (such as shell ‘Nonident P40’) in 100 ml water. 
 
Silver nitrate solution made by dissolving 0.4 g silver ni trate in 100 ml water. The solution is light sensitive 
and shall be stored in dark brown glass bottles. 
 
Application: A mixture of equal quantities of the two solutions (shel f life about one month) applied to a freshly cut surface 
produces a deep red-brown colour in wood containing pentachlorophenol (PCP). 
 
Annex C  
Method for determination of preservative retention  
 
C1 General  
The cheapest and simplest way of measuring preservative retention is by measuring the quantity of 
preservative before and after treatment of a charge and the volume of timber in the charge. These 
measurements shall be routine in any treatment operation.  This method assumes that the difference in the volumes of the treatment solution is entirely due to absorption by the treated wood, which is not strictly true 
because some solution losses take  place by leakage, spilling and dr ipping from both the treatment 
equipment and the treated timber.  Additional analytical testes may be required to confirm treatment to the required specification.  (See Clauses C2 and C3.)  
 
C2 Oil Preservatives  
 
The charge retention shall also be measured by weighing a number of sample pieces, or even all the timber 
in a charge before and after treatment.  It may also be checked as in Clause C1.  
C2.1  Retention measurements by analysis 
 
C2.1.1  Analytical sample                      KS 94:2013  
 
 
. 
 
© KEBS 2013 — All rights reserved         
     7
 Test specimens preferably consist of increment cores, or other geometrically uniform pieces, the volume of 
which can be calculated from their linear dimensions. 
 
The volume of irregularly shaped pieces shall be determined by water displacement.  
C2.1.2 Apparatus   
The apparatus assembly shown in Figure 1 consisting of an extraction flask, soxhlet extractor, water trap and a reflux condenser or cold-finger shall be used to extract the preservative solution from the wood sample.  
The same equipment shall be employed for determ ination of moisture content of treated wood. 
 The water trap shall be chemically clean so that the shape of the meniscus at the end of extraction is the 
same as at the beginning.  It may be coated from ti me to time with a silicone resin to give a uniform 
meniscus.  A thin rod of material to which water does not adhere, such as polytetrafluoroethylene, may be used to transfer water condensed elsewhere to the water layer in the trap. 
 
C2.1.3 Procedure  Sufficient toluene shall be placed in the extraction flask to fill the water trap and soxhlet extractor and to 
maintain a reservoir in the extraction flask. About 0.5 ml distilled water shall be added. The apparatus shall 
be assembled, heat applied and refluxed for about 30 minutes.  The contents of the water trap shall be allowed to cool to room temperature, then any water adhering to the walls of the condenser and water trap shall be transferred to the water layer in the trap.  The volume of water in the trap shall be noted to the 
nearest 0.01 ml. 
 The weighed test specimens shall then be placed in the soxhlet extractor and sufficient heat is applied to the 
extraction flask to reflux the toluene at the base of the condenser or cold-finger so as to operate the soxhelt 
siphon at least once every 12 minutes. The refluxing shall be continued for 5 hours to 16 hours or until no more colour is extracted from the sample, whichever is the greater. 
 
The contents of the trap shall then be allowed to cool to room temperature before transferring any water adhering to the walls of condenser and water trap to the layer in the trap.  The volume of water shall again be read to the nearest 0.01 ml. 
 
The extracted specimens shall be reweighed after drying to constant weight in a ventilated oven at 103 ± 2
ºC. 
 
C2.1.4 Calculation   
Preservative retention =vmkgm ww3
2 1 
  Moisture content  =
percentwm
2100 
 
Where, 
 
 W 1 =mass of wood pieces in g before extraction, 
 
 W 2 =oven dry mass in a g of extracted wood pieces, 
  M =volume in ml of water extracted, and  
 
 V =volume of the wood pieces in cm
3 . 
 
C3. Waterborne Preservatives 
 C3.1 Analytical sample    KS 94:2013            
 Test specimens inform of increment cores or cross-sections shall be sampled further into thin shavings or 
dust from which the preservative can be extracted by leaching. Appropriate reagents shall be reacted with 
the small wood particles to transfer the preservative in to solution. The quantities of individual ingredients in 
the solution are determined most conveniently spectrophotometrically and retention then calculated by adjusting for wood density and moisture content. 
 
The reagents employed differ according to the preserva tive, the element to be determined, and the specific 
method of instrument used to measure concentration in the solution after leaching.  Appendix D explains the 
procedure for analysis of copper-chrome-arsenic preservative treated wood by atomic absorption 
spectrophotometer but any other suitable ch emical method of analysis may be used. 
 
 
 
Annex D 
 Method for determination of copper, chromium and arsenic in preservative treated 
timber 
 
D1 Application  
 
The method is suitable for wood samples weighing up to 8 g, containing not less than 0.002 per cent of 
copper and chromium and 0.000 5 per cent arsenic.   It is suitable for determination of the elements in 
sawdust, woodflour and thin shavings.  There is no inter-elemental interference during the determination and the procedure is specific for arsenic in the presence of phosphorus compounds. 
 
D2 Reagents 
 
All reagents including water shall be of analytical reagent quality.  
D2.1  Sulphuric Acid 2.5 m  
Made by cautiously adding, with stirring and cooling, 280 ml concentrated sulphuric acid to 1 600 ml of water 
and diluting to 2 litres with water. 
 D2.2 Hydrogen peroxide solution  
100 - Volume 
 D2.3  Sodium sulphate solution   
 3 per cent made by dissolving 30 g sodium sulphate in water and diluting to one litre. 
 D2.4 Sulphuric acid/sodium sulphate solution   
Made by diluting 200 ml of the 2.5 molar sulphuric acid plus 100 ml of the 3 per cent sodium sulphate 
solution with water to one litre.  
D2.5 Standard solution  
Copper pentahydrate 0.198 5 g shall be dissolved in water and the solution transferred to a 100 ml volumetric flask.  Anhydrous potassium dichromate 0.288 g shall be dissolved in water and 10 ml of 2.5 M 
sulphuric acid and 2 ml of 100-volume hydrogen peroxide added, boiled, cooled and the mixture transferred 
to the volumetric flask.  Arsenic trioxide 0.1320 g, after drying at 103
ºC – 110ºC for 1 hour to 2 hours, shall be 
dissolved by boiling in a so lution consisting of  10 ml of 2.5 M sulphuric acid , 2 ml of 100-volume hydrogen 
peroxide and 10 ml of water, cooled and also transferred to the volumetric flask. Then 10 ml of 31 per cent 
sodium sulphate solution shall be added to the flask and diluted to the mark with water.  One ml of the standard solution is equivalent to 500, 1000 and 1000 micrograms of copper chromium and arsenic respectively. 
 
D2.5.1. Calibration Solutions  Aliquots of the standard solution shall be transferred by pipette or burette to 100 ml volumetric flasks and 
mixed after diluting to the mark with the sulphuric acid-sodium sulphate solution. 
 D2.5.2  Atomic absorption spectrophotometer operating conditions 
With small difference necessary with instruments of different manufacturer, the instrument shall be set to 
conditions listed in Table 5.                      KS 94:2013  
 
 
. 
 
© KEBS 2013 — All rights reserved         
     9
  
Table 5 
 
  
Instrument Control  Copper  Chromium  Arsenic 
Wavelength, mm 
 
Slit width, mm  
Lamp current, mA 
 Scale expansion 
 
Burner  
Burner height, mm 
 Acetylene flow rate, 
Cm
3 min. -1 at a pressure of 2.1 bar 
 
Air-flow rate, cm3 min -1 at a pressure 
of 0.7 bar 
 
Hydrogen flow rate, cm min.-1 at a 
pressure of 0.7 bar 
 
Argon flow rate, cm3 min. -1 at a 
pressure of 2.1 bar. 
 324.8 
 
0.08  
4 
 Up to X10 
 
100mm acetylene  
10 
  
1 000 
 
 5 000 
 
 - 
 
 - 357.9 or 429.0 
 
0.06 or 0.10  
8 
 Up to X10 
 
100mm acetylene  
5 
  
1 800 
 
 5 000 
 
 - 
 
 - 193.7 or 197.2 
 
0.30  
 
 Up to X10 
 
100mm propane  
14 
  
- 
 
 - 
 
 1 800 
 
 5 000 
 D2.5.3  flame ignition procedure for the argon (entrained air) hydrogen flame  
If argon and hydrogen are introduced together great diffic ulty will be experienced in igniting the mixture.  The 
argon cylinder shall be connected, via a reducing valve, to the air inlet. 
 Similarly the hydrogen supply shall be connected to the fuel inlet.  Gas lines, especially the hydrogen line, 
shall be ascertained as free from leaks and the spray chamber flushed with hydrogen. The hydrogen flow 
shall be adjusted to 1 500 cm
3 min.-1 and flame ignited.  Argon is then turned on and the flow adjusted to 500 
cm3 min.-1. 
 
D3 Procedure 
 
Ground sample shall be weighed and transferred to a 250 ml calibrated flask, 50 ml, of 2.5 M Sulphuric acid 
and 10 ml of a 100-volume hydrogen peroxide added, and heated in a water  bath at 750C for 20 minutes 
with occasional swirling to mix the contents of the flask.  The flask shall be removed from the water bath, 150 ml of water and 2 ml of the 3 per cent sodium sulphate solution added, swirled to mix, cooled to room 
temperature, diluted to the mark with water, and mixed again.  Mixing shall be repeated twice at 5-minute 
intervals.The leach solution shall be filtered through a dry 90-mm Whatman N. 44 filter paper, the first 5 ml filtrate being discarded. 
 
Using the instrument operating conditions listed in Table 5, the sulphuric acid/sodium sulphate solution shall 
be aspirated to obtain the blank absorbance, then a suitable range of calibration solutions followed by the filtrate from the sample solution. After the last sample has been run the calibration solutions shall be 
checked. From calibration graphs of the concentration of copper, chromium and arsenic against absorbance, 
concentration in the sample solution shall be determined by comparing the test solution absorbance with the calibration graphs. 
   KS 94:2013            
 This procedure is suitable for samples in the weight range of 3 g to 8 g.  For smaller samples of 100 ml, 50 
ml or 25 ml, calibrated flasks and corresponding volume of reagents shall be used.  A corresponding sample 
shall be dried in an oven for moisture content determination  
 
D4 Calculation  
Element retention  = 
wm av100   per cent of oven-dry wood 
 
where,  
a = equivalent absorbance IN g/ml of the element in the leach solution, 
 
v =volume in ml of the leach solution,  
m= moisture content in percentage of the wood sample, and  
 w=mass of the test wood sample. 
 
Annex E 
Methods for determination of moisture content of wood 
 
E1 Sample selection  
 
For average moisture content, test specimens consisting of full cross sections 15 mm to 20 mm thick shall be 
cut, not closer than 500 mm from the end of the timber piece sampled.  Alternatively, borings, perpendicular to the timber surface may be taken.  The test specimens shall be weighed immediately after extraction or put 
in air-tight containers for later weighing. 
 
E2 Procedure 
 
The weighed specimen shall be dried to constant weight in an oven at 103 ± 20 C and then reweighed.  
From the two weightings, moisture content in percentage shall be calculated from the formula: 
 
Moisture content=
22 1 100
WW W 
 
 Where, 
 
W
1=original mass of the wood sample on extraction, 
 
W2=oven-dry mass of the wood sample. 
 
E3. Other methods 
 
E3.1 Liquid extraction — For wood treated with preservative oils the appropriate method is described I 
class C2. 
 
E3.2 Direct measurement with moisture meter   
Moisture content can approximately be measured directly with an electric moisture meter.  The method is 
useful as a preliminary indication for wood at moisture content below fibre saturation point but cannot 
generally be relied on alone.  
 
  
 
Annex F 
Durability of wood poles and posts                     KS 94:2013  
 
 
. 
 
© KEBS 2013 — All rights reserved         
     11
  
F1 Meaning of wood Durability 
 
 It is common practice in describing characteristics of individual timber to include its durability, which is an 
indication of its relative resistance to natural destructive agents.  Being organic material, wood is destined for 
climatic-and bio-degradation but the period of time taken for completion of the degradation process or its 
advancement to a specific degree depends on many fact ors, the most important of which are the species of 
wood, the destruction agents involved, and the particular environment location f the material. 
 
While any wood can last indefinitely in a dry sheltered location, the same wood is sure to be destroyed soon or later in most service situations.  The most common natural agents of wood destruction are decay fungi 
and insects.  Quicker destruction takes place where these agents abound, which means in an environment 
ad does exist in soil.  Those timbers therefore which persist for a relatively long period while exposed to 
weather in contact with ground  are classified as durable.   Natural durability of diff erent timbers varies from a 
few months for some species to several decades for the most durable species.  Experience has shown that 
adequately preservative treated timber can exceed durability of the most naturally durable timber species. 
  
F3 Suitable timbers for treated poles 
 
 Unfortunately, some timbers are not easil y treatable.  Like natura l durability, trea tability of wood differs over a 
very wide range.  There are also differences between heartwood and sapwood of the same timber, the 
sapwood generally being more easily treated.  Thus of heartwood and easily treatable sapwood while a 
timber like cypress has heartwood of only moderate natural durability and sapwood fairly resistant to preservative treatment.  It is important therefore in selecting timber for preservative treatment to ascertain 
that the timber is treatable. 
 
 Among locally grown common timbers, pine, eucalypts, and casuarina are recommended as suitable for 
preservative treatment in their natural round form. 
 
Table 6ـSome examples of timbers with durable heartwood 
 
Standard Name  Botanical Name 
Muiri 
 
Muhuhu  
Cedar 
 Mbambakofi 
 
Iron bark 
 Tallow wood Prunus africana 
 
Brachylaena huillensis  
Juniperus procera 
 Afzelia quanzensis 
 
Eucalyptus paniculata 
 Eucalyptus microcorys 
 
Note; not all the examples in table 6 are commercially available. 
 
F4 Durability and service life  
 
Because of the many variables determining service life of timber, it impossible to state definitely the period 
timber in use will last. However, if naturally durable timbers are estimated to last under severe decay hazard 
situations for an average life of thirty years, timber conforming to this standard should last equally as long. 
  
 
  
 
   KS 94:2013            
 Annex G (informative) 
Mass spectrometry 
 
G1 Mass Spectrometry is the science of displaying the spectra  of the masses of the molecules comprising a 
sample of material. It is used for determining the elem ental composition of a sample, the masses of particles 
and of molecules and for elucidating the chemical structures of molecules such as peptides and other chemical compounds. 
 
G2 Mass Spectrometry works by ionizing chemical compounds to generate charged molecules or molecule 
fragments and measuring their mass-to-charge ratios.  In typical a typical MS procedure: 
1. A sample (which may be solid , liquid or gas) is ionized. 
2. The ions are separated according to their mass-to-charge ratio 
3. The ions are dynamically detected by some mechanism capable of detecting energetic charged 
particles. 
4. The signal is processed into the spectra (singular spectrum) of the masses of the particles of that 
sample. 
 
G3 The elements or molecules are identified by correlating known masses by the identified masses.A mass 
spectrometer instrument will consist of four modules. 
a) An ionizer converts some portion of the sample into ions. These are a wide variety of techniques for 
this, depending on the phase (solid, liquid, gas) of the sample and the efficiency of various ionization 
mechanisms for the target species in question. 
 Mass spectrometers are generally named after the ion source used e.g. 
 Electron ionization 
 Glow discharge mass spectrometry (GDMS) 
 ICPMS 
 Resonant ionization mass spectrometry (RIMS) 
 SIMS 
 TIMS 
b) An extraction system which removes ions from the sample and gives them a trajectory which allows 
the mass analyzer to transmit them 
c) A mass analyzer sorts the ions by mass 
d) A detector, which measures the value of an indicator quantity and thus provides data for calculating 
the abundance of each ion present. Some detectors also give special information e.g.  a multi-
channel plate. The technique has both qualitativ e and quantitative uses. These include identifying 
unknown compounds, determining the isotopic composition of elements in a molecule and 
determining the structure of a compound by observing its fragmentation.  
 Other uses include identifying the amount of a compound in a sample or studying the fundamentals 
of gas phase ion chemistry (the chemistry of ions and neutrals in a vacuum)