|Ahead of print publication
Gaseous pollutants in Indian EKM and SSK class submarines
Vivek Verma1, Nimesh Tarway2, Anil Pinninti3
1 Officer-In-Charge, School of Naval Medicine (SNM), INHS Asvini, Mumbai, Maharashtra, India
2 Classified Spl (Medicine) and Gastroenterology, Department of Gastroenterology, INHS Asvini, Mumbai, Maharashtra, India
3 Resident (DMM), School of Naval Medicine (SNM), INHS Asvini, Mumbai, Maharashtra, India
|Date of Submission||17-Sep-2019|
|Date of Decision||11-Jan-2020|
|Date of Acceptance||25-Nov-2020|
|Date of Web Publication||01-Apr-2021|
INM, INHS Asvini, Colaba, Mumbai - 400 005, Maharashtra
Source of Support: None, Conflict of Interest: None
Introduction: Once a submarine dives, the captive atmosphere inside keeps changing due to release of various pollutant gases. The gases are produced by machinery, cooking, human, paints, batteries, cooking etc. The study was envisaged to measure these gaseous pollutants on surface and in prolonged dive onboard EKM and SSK class submarines. Methods and Material: Detector tubes and pumps were used to measure the concentration of twenty gaseous pollutants in harbour on surface & during sailing in dived condition. In harbour, readings were taken early morning and before secure in the evening. During sailing readings were taken on surface, just after diving and thereafter every four hrs. The readings were recorded in excel sheet and correlated with activities on board at time of taking reading. Results: Only Ammonia and Hydrogen Sulphide were detected at the beginning of the day in harbour, however by the end of the day all other gases were detected except Mercury, Oil mist, Nitrogen Dioxide, Ozone & Arsine. At Sea none of the gases were detected at the beginning of sailing. At 12h post dive all gases were detected except Mercury, Oil mist, Nitrogen Dioxide, Ozone, Halogenated Hydrocarbons & Arsine. Recommendations and Conclusion: The gas concentration values obtained by using detector tubes and pumps were found to be within recommended Permitted Exposure Levels (PEL) for human for continuous exposure. No gas was found to be above the recommended PEL. There was no significant difference in the gas concentration levels in the submarineWs of Russian origin and German origin. Pump and detector tube is a convenient, reasonably accurate and efficient method to measure gaseous pollutants on board Submarines.
Keywords: Detector bellow pump, detector tubes, gaseous pollutants, submarine
| Introduction|| |
Worldwide, there have been 102 known incidences in which submarines have become disabled and have sunk in noncombat situations, leading to a loss of approximately 2600 lives. The most probable cause of a submarine sinking is flooding caused by an event that breaches the outer hull. It is likely that such an event would also start a fire within the submarine. The immediate concern for the crew is the release of toxic gases that are produced as a result of combustion of various material on-board submarine. Human exposure to these gases can lead to adverse health effects, particularly Respiratory and Central Nervous System effects. These effects are nonspecific symptoms such as generalized malaise, headache, irritation, redness and watering of eyes, and decreased efficiency.
The main sources from which these pollutants are generated are diesel engines, batteries, sanitary systems, human beings, paints, refrigeration systems, etc. The various pollutant gases include carbon dioxide, carbon monoxide, hydrogen, arsine, oxides of nitrogen (NO2, NO), stibine, chlorine, H2SO4 aerosols, sulfur dioxide (SO2), hydrogen sulfide (H2S), ammonia (NH3), hydrocarbons, and Freon. At present, only a few of these gases are measured inside submarine atmosphere regularly like oxygen, carbon dioxide, and hydrogen. There are only a few studies where presence of other possible gases has been explored in the Indian Naval submarines and the data regarding studies conducted in foreign naval submarines are scarce and are not available in the public domain. The levels of these gases are controlled by regular ventilation, filters installed in the ventilation system, absorption of carbon dioxide, and regeneration of oxygen using the regeneration cartridges.,
To detect and quantify various possible contaminants, this study was planned and the levels of selected 20 pollutants were measured inside various compartments of EKM as well as SSK class of submarines. The measurements were taken in harbor as well as during sailing in a dived state using the detector tubes and pumps (Draeger make).,, The results were analyzed as to whether a pollutant was detected/not detected. The concentration, whether concentration increased/not, during the day or after diving. Any significant difference between two classes of submarines. Whether concentrations were within the Permissible Exposure Limits (PELs) or not.
| Materials and Methods|| |
Detector tubes and pumps (Draeger, Germany make) were used to measure the concentration of various gaseous pollutants. A detector tube is a hermetically sealed glass tube containing an inert solid or granular material such as silica gel, alumina, resin, pumice, or ground glass. The inert material is impregnated with or mixed with one or more reagents which change color when specific types of air contaminants are introduced. The length of the color change or stain or the intensity of color change as compared to comparative standards indicates the amount of material present. It can be specific to a chemical or detect a general family of gases. It can measure low/sub ppm levels to Vol. %. Its accuracy varies from + 5% to + 25% depending on gas and measuring range. A typical detector tube is shown in [Figure 1]. Draeger tubes are calibrated at an atmospheric pressure of 1013 hPa (i.e., 1013 mbar). To correct for the influence of pressure, the value read from the tube scale must be multiplied by the correction factor, equal to 1013 hPa/actual atmospheric pressure in hPa. Draeger-tubes should be stored and used in a temperature range of 35°F–77°F. Tubes should not be subjected to direct sunlight for prolonged periods. The tubes are used with a detector pump which is made up of a rubberized material and the one used for this study was Draeger gas Detector pump Accuro. It weighs 225 g approximately and its dimensions are 85 mm × 170 mm × 45 mm. It is used for short-term measurements of the pollutants with a small number of strokes. The pump is small and easy to handle inside enclosed spaces. It has a distinct end-of-stroke indicator, automatic stroke counter. There is no frictional wear and tear of parts and leakage is not a problem. Its leak test is simple and it has a faster opening time per stroke. A typical accuro pump is shown in [Figure 2]. The readings were taken in the harbor as well as during the sailing time. The measurements were taken in three compartments inside the Russian origin submarines (EKMs) and two compartments in German origin submarines (SSKs). In harbor, measurements were taken once at the start of the working time and once at the end of the day. During the sailing time, these measurements were taken every 04 h after diving and 04 readings were taken before the submarine was required to do snorting because of the build up of carbon dioxide. The exact schedule of recording readings is given in [Table 1]. The number of strokes required for various pollutants is specific for each tube. The readings were taken in the compartments in specific places where the chances of picking up the pollutants were maximum, for example, CO, SO2 in the engine room, oil mist in the galley, and H2S in the compartment where the sanitary system is located. The reading was also analyzed for their association with a particular activity being undertaken onboard.
| Results|| |
The levels of various pollutants are tabulated in [Table 2] and [Table 3]. Certain common observations are enumerated below:
Detector tubes and pumps were found to be a very convenient method of pollutant detection except for a very few tubes for which the number of strokes is very high (40–100). The bellow pump is very convenient to use, but sometimes, the automatic reader skips counting of stroke so a visual check on the number of strokes should also be kept. The levels of all the pollutants were found to be within the PEL, a very few pollutants were found to be above the minimum detectable concentration (MDC).
| Discussion|| |
The captive atmosphere inside a submarine has many gaseous pollutants. Human exposure to these pollutants can lead to adverse health effects, particularly cardiorespiratory and central nervous system effects.
These gases are present inside the submarine atmosphere even during normal operation as they are released from the batteries, engines, crash dives, cooking, sanitary system, and human beings, though their concentration is often less than, which can lead to symptoms. The recommended levels for exposure are those recommended by various agencies for exposure of workers in the industry.,, A very few pollutants have been checked for their effects based on the exposure levels and the actual time inside a submarine atmosphere during simulated conditions of fire and flooding.
A committee was formed in the year 2002 in the USA to review the levels of certain selected chemicals which recommended submarine escape action levels (SEAL) for these chemicals. These chemicals along with their recommended exposure levels are given in [Table 4]. The subcommittee further recommended that simultaneous exposure to irritant gases like ammonia, chlorine, hydrogen chloride, nitrogen dioxide, and sulfur dioxide is additive and not synergistic. The subcommittee recommended that hydrogen sulfide should be considered an irritant gas. The subcommittee also recommended that a separate continuous exposure index (CEI) should be established for carbon monoxide and hydrogen cyanide because the effects of exposure to these gases may be additive as well. If future research conducted on the health effects from exposures to mixtures of gases shows that the effects are not additive, then the CEI approach will have to be modified accordingly. Another committee was formed in the USA to define emergency and continuous exposure guidance levels for selected submarine contaminants, it recommendations were published in the year 2008.
|Table 4: Comparison of the US navy's proposed submarine escape action levels s with the subcommittee's recommended submarine escape action levels|
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In our study, the levels of all of the pollutants were found to be below the PEL. A few pollutants such as ammonia, alcohol, CO, H2S, xylene, and toluene were found to be slowly building up during the dive time. The buildup was very slow and the gaseous pollutants were not detected in the first 04 h of dive.,,,, Each of the 20 gases studied has varied effects on human beings depending on the concentration, time of exposure, and presence of other pollutants, describing all these here would not be feasible. The WHO lays down the exposure limits for these chemical gases, which can be safely used for industrial purpose. However, for purpose of submarines, each country has to develop its own values depending on the conditions peculiar to their submarines. A few pollutants such as ammonia and H2S which were detected during the harbor measurements were not detected in the initial reading at sea, most likely because of the continuous ventilation onboard during the initial period of sailing. A few pollutants like H2SO4 fumes were detected after evolution like major cleanship because of the use of spirit onboard.,,, Hence, it is recommended that such chemicals should be used with due care in the submarines. Chlorine is another important gaseous pollutant which can lead to a number of health effects.,
Most of the Drager-tubes had graduated markings on them and were easy to use, but a few like hydrocarbon ones did not have any markings and the readings had to be taken based on the discoloration and number of strokes. Some tubes required as much as 100 strokes for one measurement which is a cumbersome and time-consuming procedure. The automatic counter of the Drager pump counts the strokes but sometimes skips the counting, so a visual check should also be kept on it.
At present, four types of air purification filters are used in the submarines anti-aerosol filter, catalytic filter, adsorbing filter, and combined filter. The details regarding these filters are available in the book of reference on filters provided by original equipment manufacturer. These filters have a defined life based on the time it is put into use and the flow of air through it, as recommended for effective operation. This study indicated that the current practice of replacing these filters after the stipulated time is quite effective in keeping the levels of these pollutants in control under normal operating conditions. However, the ventilation schedule will have to be modified if more than the recommended number of personnel are carried onboard or there is fire or flooding.
Further studies can be conducted to study the effects of environmental conditions (e.g., humidity, temperature, pressure) found on a disabled submarine on the buildup and toxicity of the gases. Fire on a disabled submarine will generate gaseous and particulate matter, studies can be conducted to identify these particulate matters and effects of these. The Subcommittee on SEAL also recommended crew members wearing emergency breathing apparatus to remove them each hour, as concentrations of some of the gases should decrease over time because of contact with the wet surfaces likely to be found in a disabled submarine. That same logic leads the subcommittee to recommend that the concentrations of all gases be determined as frequently as possible. The recommended SEALs are for normal atmospheric conditions (an atmospheric pressure of 1 Atmospheres Absolute (ATA) and a temperature of 25°C). Values obtained for gas concentrations using Dräeger-tubes in a disabled submarine might need to be corrected to an atmospheric pressure of 1 ATA and 25°C.
Currently, detector tubes are the only means available on submarines for measuring gas concentrations once the spectrophotometers stop functioning because of power loss. A new tube is required for each measurement of an individual gas. This makes it an expensive method of measurement; however, there are no maintenance requirements as with fixed/portable battery-operated analyzers or a gas chromatograph. It is recommended that battery-operated analyzers with specific sensors should be used for use in submarines to more accurately measure commonly found gases and allow for frequent economical measurement of the gases.
Limitations of the study
The study had the following limitations:
- The ideal method to accurately check the level of gaseous pollutants is by use of gaseous chromatograph; however, the equipment is large and it is difficult to carry it onboard. Therefore, gas samples are collected in glass tubes and brought ashore for analysis. In our study, due to nonavailability of gas chromatograph and practical superiority of detector tubes, the detector tube and pumps were used
- A record of humidity, temperature, and pressure during measurements was not done along with readings of gases, which possibly might have caused minor variations in the measured values.
| Recommendations and Conclusion|| |
The gas concentration values obtained by using detector tubes and pumps were found to be within recommended normal limits for human for continuous exposure. No gas was found to be above the recommended PEL. There was no significant difference in the gas concentration levels in the submarines of Russian origin and German origin. Detector tubes and pumps were found to be very convenient method of pollutant detection in enclosed spaces; however, number of strokes is very high (40–100) for certain gases which consumes excess time. If frequent measurements are required like in a disabled submarine, it will be very expensive and time-consuming method. Hence, a portable small size battery-operated analyzer will be a better choice for multiple measures of common gases. The Draeger bellow pump is very convenient to use but sometimes the automatic reader skips counting of strokes, so a check on the number of strokes should also be kept. A very few contaminant gases were found to be more than the MDC. Activities like major cleanship, blowing of sanitary system and venting, diving, smoking during snorting leads to detection of pollutants like H2SO4, H2S, CO respectively. The levels of H2SO4, H2S, CO, benzene, and xylene should be measured only if submarine dives for an extended period. The present methods of environmental control are sufficient enough to keep the concentration of pollutants under control during normal working conditions. A few studies carried out in the USA have shown the presence of hydrogen chloride and hydrogen cyanide under simulated conditions of a disabled submarine, so their levels can also be measured in case of an accident onboard a submarine or in a DISSUB situation. Most of the reference limiting values available for exposure to these pollutants are for an 8 h exposure for industrial workers. Some values are available as time-weighted average and a very few values are available for actual continuous exposure limits inside a submarine. In future studies, endeavor should be made to study concentration build up during longer dives and to objectively quantify the effects of these gaseous pollutants on human body by laboratory measurements.
Financial support and sponsorship
The study was funded by AFMRC.
Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2]
[Table 1], [Table 2], [Table 3], [Table 4]