TBS/MMDC 2(650 1) P3 
 
 
© TBS 2020                                                                                                                             First edition  
 
DRAFT TANZANIA STANDARD  
 
 
 
 
Ventilation in underground mines - Part 1: Air quality requirements  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
TANZANIA BUREAU OF STANDARDS  
   
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© TBS 2020                                                                                                                             First edition  
 0 Foreword  
This draft Tanzania Standard is being prepared by the Mine Planning Operations and Services Technical 
Committee (MMDC 2) under the supervision of  Mining and Minerals Standards Divisional Committee 
(MMDC).  
Currently, this draft Tanzania Standard consists o f two parts as shown in the bullets below, under the 
general title “Ventilation in underground mines”;  
 Part 1: Air quality requirement  
 Part 2: General guideline  
Other parts of the standard may be developed later if the needs arise.  
 
In preparation of this draft Tanzania standard assistance was derived from the following documents;  
 Ventilation in underground mines and tunnels – Approved code of practice of 2014 developed by 
WorkSafe New Zealand,  
 U.S. Code of federal regulations - Title 30 Mineral Resources p ublished in 2018 by Office of the Federal 
Register  
 
 
1 Introduction  
Mine Ventilation refers to supply of fresh air and removal of the diluted air/polluted air out of the mine, it can 
be supplied in mine and removed either naturally or artificially. The need of supply of air provides oxygen 
to personnel and equipment to ensure the safety of lives of people working in underground mine. Besides, 
supply of air dilute s toxic gases, dusts and emission resulting from production and control humidity and 
temperature. Therefore, the c oncentration limits for exposure of people and equipment have to be set for 
different type of mines including th ose mining  coal and metalliferous. Pollutants of air in underground mines 
include dust and a combination of many other potential  hazards, such as toxic or flammable gases, heat, 
humidity, and radiation. It is important to enhance employee safety, comfort, health, and morale in order to 
ensure effective working. This can be attained by making sure that the contaminants are not allow ed to 
exceed mandatory threshold limits imposed by standards and regulations.  
 
Coal mines and metalliferous mine have different levels of contaminants allowed for exposures of mine 
workers and equipment. The contaminants vary  from one mine to the other  based on size of the mine, 
number of workers and machines working in the mine, temperature and level of emissions.  
 
 
2 Scope  
The Tanzania Standard gives requirements including specifications of acceptable quality of air in 
underground mines. The requirements ar e established with the aim of protecting  health and safety of  
personnel working in underground min ing environment. This standard gives air quality requirements for 
both coal and non -coal underground mines.  The contents of this Tanzania standard shall not a pply to 
tunneling in the construction industry . 
 
 
3 Normative references  
The following standards are referred to in the text in such a way that some or all of their content 
constitutes requirements of this document;  
 TZS 2074 – 4 Glossary of mining terms – part 4: Ventilation  
 TZS 845  Air Quality – specifications  
 
 
4 Terms and definitions  
For the purpose of this standard the definitions contained in TZS Glossary of mining terms – part 4: 
Ventilation shall apply. Also, the following definition shall apply for the term below;  
 
4.1 Working face  – the place at which mining is being done in a heading, drift, adit, airway, chute , 
crosscut, etc.   
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4.2 Longwall working face  – a working face  in the mine in which  flat-bedded deposits  are mined through  
advanc ing over a co nsiderable width at one time  
 
4.3 Wet bulb temperature  - the temperature read by a thermometer covered in water -soaked cloth (wet -
bulb thermometer) over which air is passed . 
 
 
5 General requirements  
5.1 Exposure limits for airborne contaminants.  
Except as provid ed below, the exposure to airborne contaminants shall not exceed, on the basis of a time 
weighted average, the threshold limit values stated in TZS 845.  
Fresh air contains the following gases at the lowest practicable level and at no more than the followin g 
levels  
 
 Table1:  Time -weighted average exposure (ppm)  Short -term exposure limit (ppm)  
Pollutants  Time -weighted average exposure  Maximum allowable  Short -
term 
exposure 
limit 
Carbon dioxide  5000   5000 30000  
Carbon monoxide  50 100 300 
Hydrogen sulphid e 10 20 15 
Nitrogen dioxide  (NO 2) 3 5 5 
Nitric oxide  (NO) 25 25 35 
Nitrous oxide (N 2O) 100 25  
Sulphur dioxide  2 10 5 
Ammonia  (NH 3) 25 50 35 
Methane  (CH 4)  10000   
Asbestos  
(fibres/milliliter per 
hour)  0.1 2  
 
 
Where:  
 
Time -weighted average exposure is calculated as follows:  
  
 
 
Short -term exposure limit means the average exposure measured over any 15 -minute period in the 
working day.  
 
 
 
5.2 Quantity and velocity of air  
The mine manager must ensure that an adequate quantity and velocity of air is delivered to the working 
face of any production or development place, and within the roadways leading to any working face,  
workshops, shaft stations, magazines and other underground areas where personnel can be found  to dilute 
and render harmless any accumulations or layerin g of airborne contaminants.  
 
The volume of air passing through an active working face, other than a longwall working face, is not less 
than 0.3 cubic metres per second for each square metre of normal development cross -sectional area and 
 
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© TBS 2020                                                                                                                             First edition  
 the volum e of air passing through an active longwall working face is not less than 4 cubic metres per second 
for each metre of extracted height in the face.   
 
The mine manager must ensure, in respect of any underground parts of a mining operation where a mine 
worke r is doing work or may travel, that the air in that part is provided at an adequate quantity and velocity 
to ensure the mine worker will not be exposed to a concentration of dust that is likely to cause harm to the 
mine worker.  
 
5.3 Heat and humidity  
The mine manager  should ensure that the temperature, humidity and air velocity are controlled underground 
so that mine workers are not  severely stressed by the  exposure to extreme heat, humidity or cold.  
This includes the development of a program  for the co ntrol of  heat stress.  
 
Intervention measures are required when the wet bulb t emperature increases above 25°C.Some of the 
intervention  measures are indicated in the Table 2 . 
 
 
Table 2: Intervention measures to be taken by the min e at certain temperature/humidity levels.  
Temperature  Action  
Wet bulb > 25°C  An air velocity of not less than 0.5 metres per second  
should be provided.  
Effective 
Temperature  >30°C  The mine manager should ensure mine workers do  not work in the 
mine unless carrying out work in an emergency  situation in 
accordance to Standard Operating Procedure s. 
 
 
The mine manager should ensure there is a procedure available at the mine or tunnel to determine the 
Effective Temperature . 
 
 
 
5.4 Methane levels  
5.4.1  Gas emissions  
Gases  released from the surrounding rock or other sources may be suffocating, toxic or explosive, and 
some may have both toxic and explosive properties.  
 
Although the release of methane  is not commonly experienced in metalliferous mines and tunnels, it can 
occu r, and the mine manager  should ensure that appropriate monitoring and control measures are in place 
for the early detection of such gases.  
a) If the level of methane exceeds 1% by volume, all non -safety critical electrical and diesel equipment 
in the place where the level is exceeded should be de -energized, shut down or switched off.  
b) Where the level of methane in the air is 2% or more by volume, all mine workers in that part of the 
mine should be withdrawn to the surface or a place of safety.  
c) Access to the a ffected area should be prevented with a secure barricade or fence that is clearly 
marked with  danger tape and sign post written “DANGER - DO NOT ENTER’’ to prevent access.  
d) In a mine or tunnel where monitoring identifies that gas released from the surrounding rock is a 
risk, the mine manager should ensure that the Ventilation Control Plan includes control measures 
such as:  
i. Sealing of the surrounding rock.  
ii. Closure and sealing of the problem area of the mine.  
iii. Draining off the gases to exhaust.  
iv. Pressur izing the area to contain gases in the surrounding rock.  
v. Dilution of gases to harmless levels by increased ventilation volumes.   
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 vi. Absorption by water percolation and spraying.  
vii. Monitoring systems with appropriate alarms.  
e) In a mine or tunnel where gas being re leased from the surrounding rock is likely to occur, all mine 
workers should be trained in how to identify the hazard, the need to immediately report an 
occurrence, and procedures for the use of personal respiratory protection or refuge chambers, in 
the ev ent that hazardous gas is identified as being released into the underground atmosphere.  
 
 
6 Air quality requirements  for underground metal and nonmetal mines  
Mine manager shall ensure a ir in all active workings  of an underground mine contain at least 19.5 vo lume 
percent oxygen.  
 
6.1 Exposure limits for airborne  contaminants.  
The exposure to airborne  contaminants shall not exceed,  on the basis of a time weighted average,  the limit 
values listed in the TZS 845: 201 2 
 
 
6.2 Exposure monitoring.  
Mine manager should ensure  dust, gas, mist, and fume surveys  are conducted  at least once per month to 
determine the  adequacy of  control measures.  
 
6.3 Control of exposure to airborne contaminants.  
Control of employee exposure to  harmful airborne contaminants shall  be, insofar as feasible, by  prevention 
of contamination, removal by exhaust  ventilation, or by dilution with  uncontaminated air. However, where  
accepted, engineering control measures  have not been developed or when necessary  by the nature of work 
involved  (for example, w hile establishing controls  or occasional entry into hazardous  atmospheres to 
perform maintenance  or investigation), employees  may work for reasonable periods of  time in 
concentrations of airborne contaminants  exceeding permissible levels  if they are protec ted by appropriate  
respiratory protective equipment.  
Whenever respiratory protective equipment  is used a program for selection,  maintenance, training, fitting, 
supervision,  cleaning, and use shall meet the  following minimum  requirements:  
a) Approved r espirators which are applicable  and suitable for the purpose intended  shall be furnished and 
miners  shall use the protective equipment in  accordance with training and instruction.  
b) A respirator program consistent  with the requirements of ISO/TS 16975 -1:2016  
c) When respiratory protection is  used in atmospheres immediately  harmful to life, the presence of at least  
one other person with backup equipment  and rescue capability shall be required  in the event of  failure 
of the respiratory  equipment.  
 
6.4 Exposure to particulate matters  
6.4.1  Respirable dust standard.  
Each operator shall continuously  maintain the average concentration of  respirable dust in the mine 
atmosphere  during each shift to which each miner  in the active workings of each mine is  exposed, as  
measured wi th an approved  sampling device and expressed in terms  of an equivalent concentration, at or  
Below  1.5 mg/m3. 
 
6.4.2  Respirable dust standard when crystalline quartz is present.  
(a) Each operator shall continuously  maintain the average concentration of  respirable  quartz dust in the  
mine atmosphere  during each shift to which  each miner in the active workings of  each mine is exposed at 
or below 0. 4 mg/m3 (400 micrograms per cubic meter  or μg/m3) as measured with an approved  
sampling device and expressed in terms  of an equivalent concentration.  
 
(b) When the equivalent concentration  of respirable quartz dust exceeds  100 μg/m3, the operator shall 
continuously  maintain the average concentration  of respirable dust in the mine atmosphere  during each 
shift to which each miner in the active workings is  exposed as measured with an approved  sampling device  
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© TBS 2020                                                                                                                             First edition  
 and expressed in terms  of an equivalent concentration at or  below the applicable standard. The  applicable  
standard is computed by dividing  the percent of quartz into the n umber  10. 
 
6.4.3  Respiratory equipment; respirable dust.  
Approved Respiratory equipment shall be made available to all persons . Use of respirators shall not be 
substituted for environmental control measures in the active workings. Each operator shall maintain an  
adequate supply of respiratory equipment.  
 
When required to make respirators available, the operator shall provide training prior to the miner’s  
next scheduled work shift, unless the miner received training within the previous 12 months on the types of 
respirators made available. The training shall include: The care, fit, use, and limitations of each type of 
respirator.  
 
An operator shall keep a record of the training at the mine site for 24 months after completion of the training. 
An operator may keep the record elsewhere if the record is immediately accessible from the mine site by 
electronic transmission.  
 
 
6.4.4  Respiratory  equipment; gas, dusts, fumes, or mists.  
Approved Respiratory equipment shall be provided to persons exposed for short periods to inhalation 
hazards from gas, dusts, fumes, or mists. When the exposure is for prolonged periods, other measures to 
protect suc h persons or to reduce the hazard shall be taken.  
 
 
6.4.5  Selection, fit, use, and maintenance of approved respirators.  
In order to ensure the maximum amount of respiratory protection, approved respirators shall be selected, 
fitted, used, and maintained in accor dance with Tanzania  Standard s.  
 
6.5 Air quality detectors and measurement devices . 
(a) Tests for methane shall be made by a qualified person with approved detectors that are maintained in 
permissible and proper operating condition and calibrated with a known methane -air mixture  as frequent 
as required by mine manager. The records shall be kept in monthly basis . 
 
(b) Tests for oxygen deficiency shall be made by a qualified person with  oxygen detectors that are 
maintained in permissible and proper operating cond ition and that can detect 19.5 percent oxygen with an 
accuracy of ±0.5 percent. The oxygen detectors shall be calibrated  before measurement . 
 
(c) Handheld devices that are used for measuring air velocity, carbon monoxide, oxides of nitrogen, and 
other gase s shall be  maintained in permissible and proper operating condition.  
 
(d) Maintenance of instruments required by paragraphs (a) through ( c) of this section shall be done by 
persons trained in such maintenance.  
 
6.6 Prevention of gas explosion other than methan e. 
For the purpose of preventing explosions from gases other than methane, the following gases shall not be 
permitted to accumulate in excess of the concentrations listed below:  
(1) Carbon monoxide (CO) —2.5 percent  
(2) Hydrogen (H 2)—0.80 percent  
(3) Hydrogen sulfide (H 2S)—0.80 percent  
(4) Acetylene (C 2 H2)—0.40 percent  
(5) Propane (C 3 H8)—0.40 percent  
(6) MAPP (methyl -acetylene -propylene -propodiene) —0.30 percent   
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6.7 Restricted use of chemicals.  
Chemical substances  that can result into contamination of underground air shall  not be used or stored 
except under conditions approved by  relevant government regulatory authority . 
 
 
6.8 Radiation  
6.8.1  Radon daughter exposure monitoring.  
a) In all mines at least one sample  shall be taken from exhaust mine air by a  competent person to  
determine if concentrations  of radon daughters are  present.  
If concentrations  of radon daughters in excess  of 0.1 work level (WL)  are found in an exhaust  air sample, 
thereafter — 
i. Where uranium is mined —radon  daughter concentrations representative  of worker’s breathing zone 
shall be determined  at least every two weeks at  random times in all active working  areas such as 
stopes, drift headings,  travelways, haulageways, shops, stations,  lunch rooms, magazines, and any  
other place or location where pers ons work, travel, or congregate. However,  if concentrations of radon 
daughters  are found in excess of 0.3 WL in an active  working area, radon daughter concentrations  
thereafter shall be determined  weekly in that working area  until such time as the weekly d eterminations  
in that area have been 0.3  WL or less for 5 consecutive weeks.  
ii. Where uranium is not mined — when radon daughter concentrations  between 0.1 and 0.3 WL are found 
in an  active working area, radon daughter  concentration measurements representative  of worker’s 
breathing zone  shall be determined at least every 3  months at random times until such  time as the 
radon daughter concentrations  in that area are below 0.1 WL, and  annually thereafter. If concentrations  
of radon daughters are found in excess  of 0.3 WL in an active working area radon daughter 
concentration  thereafter  shall be determined at least weekly in that working area until such  time as the 
weekly determinations in  that area has been 0.3 WL or less for  5 consecutive weeks.  
 
b) If concentrations  of radon daughters  less than 0.1 WL are found in an  exhaust mine air sample, 
thereafter:  
i. Where uranium is mined —at least  one sample shall be taken in the exhaust  mine air monthly.  
ii. Where uranium is not mined —no further exhaust mine air sampling is  required.  
 
c) The sample date, locations, and  results obtained under (a) and (b) above  shall be recorded and 
retained at the  mine site or nearest mine office for at  least two years and shall be made  available for 
inspection.  
 
6.8.2  Annual exposure limits.  
No person  shall be permitted to receive  an exposure in excess of 4 work level month ( WLM ) in any calendar 
year.  
 
6.8.3  Maximum permissible concentration.  
Persons shall not be exposed to  air containing concentrations of radon  daughters exceeding 1.0 WL in 
active  workings . 
 
 
6.8.4  Respirators.  
In environments exceeding 1.0 WL,  miners shall wear respirators approved for radon daughters  
 
6.8.5  Posting of inactive workings.  
Inactive workings in which radon  daughter concentrations are above 1.0WL, shall be posted against 
unauthorized  entry  and designated by signs indicating  them as areas in which approved  respirators shall 
be worn.  
  
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 6.8.6  Protection against radon gas.  
Where radon daughter concentrations exceed 10 WL, respirator protection against radon gas shall be 
provided in addition to protect ion against radon daughters. Protection against radon gas shall be provided 
by supplied air devices or by face masks containing absorbent material capable of removing both the radon 
and its daughters.  
 
6.8.7  Gamma radiation surveys.  
(a) Gamma radiation surveys s hall be conducted annually in all underground mines where radioactive ores 
are mined.  
 
(b) Radiation  measurements are in excess of 2.0  milliroentgens per hour in the working  place, gamma 
radiation dosimeters  shall be provided for all persons  affected,  and records of cumulative individual  gamma 
radiation exposure shall  be kept.  
 
(c) Annual individual gamma radiation  exposure shall not exceed 5 rems.  
 
 
6.9 Diesel particulate matter  
 
6.9.1  Limit on exposure to diesel particulate matter.  
a miner’s  personal exposure to diesel particulate  matter (DPM) in an underground mine  must not exceed 
an average eight -hour equivalent full shift airborne concentration  of 160 micrograms of total  carbon per  
cubic meter of air (160 TC μg/m3). 
 
6.9.2  Fueling practices.  
Diesel fuel used to power equipment  in underground areas must not  have a sulfur content greater than 50 
ppm. 
 
6.9.3  Miner training.  
(a) Mine operators must provide annual  training to all miners at a mine  covered by this part who can 
reasonably  be expected to be exposed to diesel  emission s on that property. The training  
must include — 
i. The health risks associated with  exposure to diesel particulate matter;  
ii. The methods used in the mine to  control diesel particulate matter concentrations;  
iii. Identification of the personnel responsible  for maintaining those controls;  and 
iv. Actions miners must take to ensure  the controls operate as intended.  
(b) An operator must retain a record  at the mine site of the training required  by this section for one year  
after completion of the training.  
 
 
6.9.4  Diesel part iculate records.  
Table 3 lists the records the operator  must maintain and the duration for  which particular records need to 
be retained.  
 
Table 3: Diesel Particulate Matter Recordkeeping Requirements  
 Record  Retention time  
1.  Approved application for extension of time to  
comply with exposure limits.  Duration of extension  
2.  Identity of physician  or other health care 
professional and most recent written 
determination  of miner’s ability to wear a 
respirator.  Duration of miner’s employment plus 6 months  
3.  Purchase records noting sulfur content of diesel  
fuel. 1 year beyond date of purchase   
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 4.  Maintenance log  1 year after date any equipment is tagged.  
5.  Evidence of competence to perform 
maintenance.  1 year after date maintenance performed.  
6.  Annual training provided to potentially exposed  
miners.  1 year beyond date training completed.  
7.  Record of corrective action  Until the corrective action is completed.  
8.  Sampling method used to effectively evaluate a  
miner’s personal exposure, and sample results.  5 years from sample date.  
 
 
7 Air quality requirements for underground coal mines  
 
7.1 Airborne contaminants  
 
7.1.1  Emission limits for permissible  diesel -powered equipment.  
Each piece of permissible diesel -powered equipment introduced into an  underground area of an 
underground  coal mine must emit  no more than 2.5 grams per hour of diesel  particulate matter.  
 
7.1.2  Emission limits for nonpermissible  heavy -duty diesel -powered  equipment, 
generators and compressors.  
Each piece of nonpermissible  heavy -duty diesel -powered equipment  generator or compressor in an 
underground area of an underground  coal mine must emit no more than 2.5 grams per  hour of diesel  
particulate matter.  
Notwithstanding the other provisions  of this section, a generator or  compressor that discharges its  exhaust  
directly into intake air that is coursed  directly to a return air course, or discharges  its exhaust  directly into a 
return  air course, is not subject to the  applicable requirements of this section.  
 
7.1.3  Requirements for nonpermissible  light -duty diese l-powered  equipment other than 
generators  and compressors.  
Each piece of nonpermissible  light-duty diesel -powered equipment  other than generators and compressors,  
introduced into an underground  area of an underground coal  mine must emit no  more than 5.0 grams per 
hour of diesel  particulate matter.