User manual

Intended use of equipment

Con.Da domestic gas detectors are manufactured for indoor use in: campers, domestic housing, parking sites & garages, sailboats and other domestic use. Domestic gas detectors are not intended for and shall not be used in any industrial environment, demanding hazardous area classifications, flameproof, EeX or intrinsically safe equipment.
 

Technical specifications

Different monitoring methods are available for different gases and vapours. Not all gases and vapours can be monitored equally well using the same sensing technology. Each gas has its own physical properties, and one technology working well for one gas, may not necessarily work well for a different gas. Main gas sensor technologies are: Semiconductor sensors, Infra red sensing, Electrochemical cells, Pellistors, and thermal conductivity cells.
 
Domestic gas detectors use semiconductor sensors, as gas sensing element.  A semiconductor sensor, is essentially a bridge circuit, heated to approx 300 degrees centigrade. The measuring gas is absorbed onto the semiconductor sensor and its resistance change, proportionally to the gas concentration. Different types of semiconductor material are used for different gases.
 
We generally consider two different types of gases. Toxic gases and flammable gases. A sensor for a particular gas may also react and respond to other gases, and care should be taken to understand the environment and the reaction of a gas detector.
 

Carbon Monoxide is a toxic gas:

CO. Threshold limit 50ppm. Hazardous limit 400 ppm / 1 hour. Lethal concentration 1000 ppm. Carbon Monoxide is odourless and colourless and it is the most abundant toxic gas. CO has similar density to air, and gas detectors should be installed mid room at head level. Any process where there is incomplete combustion of carbon fuel, leads to the production of carbon monoxide. Eg. Petrol and diesel engines, gas and oil boilers etc.
 

Flammable gases / concentration.

%LEL lower level in air

%UEL highest level in air
 
Methane;
CH4
%LEL 4,5 
%UEL 75
Natural gas; 
 
%LEL 3,8 – 6,56  
%UEL 13 – 17
Propane;
C3H8
%LEL 2,1  
%UEL 9,5
 

Installation

Instructions for use 
 
When installing gas detectors it is necessary to consider the environmental circumstances.
 

Indoor / outdoor use;

Potential leak source;

Nature of gas or vapour to be detected;

Air movement and ventilation;

 

Gas behaviour.

Some gases are more heavy than air, and some gases are less heavy than air. Light gases tend to float upwards and collect under roofs and ceilings. Gases more heavy than air tend to float downwards and collect at floor level. Therefore gas detectors must be installed close to roof or ceilings when detecting gas or vapour lighter than air, and close to floor level when detecting gases or vapour more heavy than air.

 

Gas detectors must always be positioned relative to the gas it is to monitor.

 

LPG – Bhutan and Propane: best position 1 metre above floor level. These gases are heavier than air, and vapours are more common at floor level.

 

Natural gas, Methane and H2 are lighter than air, and vapours will be more common under roof. Gas detectors should be positioned 1 metre from roof.

 

CO has similar density as air, and gas detectors should be positioned at head level.

 
 

Installation

When Con.Da gas detectors are switched on, both the green LED and the red LED besides also the horn will be activated shortly. After approx. 3 seconds, the horn will turn off, and after further 30 seconds the red led will turn off. The gas detector has now reached its operating temperature and is now operative.

 

If gases are detected, the red LED will be switched on for 30 seconds. If gas vapour remains, the horn will be activated.

 

The sounding of the horn or blinking of red LED are indications that the gas detectors see vapours at critical levels. Locate immediately the cause of the alarm, and make sure to create strong air-circulation to clean out the damaging vapours.

 

Led indications

Green led: gas detector is switched on and working.
 
Red led: followed by horn. A potential high level of dangerous vapours is registered.
 
Operation: Con.Da gas detetctors are supplied as either AC 220 V / AC or DC. Gas detector is connected to either mains directly to wall installation or a DC source e.g. battery. Should battery by mistake be reversed polarised, gas detector fails to work however no permanent damage shall happen. Gas detectors always perform best when warm, and it is generally advised to leave the gas detectors switched on permanently. 
 
Test: Con.Da gas detectors are tested, by placing a lighter with gas leakage (no flame) under sensor. After approx. 1 minutes the gas detector should react and indicate alarm level. Red LED and horn are activated and remain active as long as alarm condition is present. Approx after 1 minutes after alarm situation has been deactivated the red LED shall stop.
 
Con.Da gas detector are not certified  EeX environments. They are not certified to be used in installations that by law require special equipment, or in installations hazardous to human health where malfunction of gas detector may cause dangerous conditions for human health. This unit is only a passive gas detector to be used as a warning instrument for alarm conditions.
 
Semiconductor sensors are sensitive to humidity, dampness and water evaporation. Humidity may malfunction the gas detector. Alarm conditions are likely to be delayed or missed altogether. Also high concentration of cigarette smoke is likely to change the function of gas detector.
 
Spray bottles that contain silicone, will cause complete breakdown of gas detector. Silicone creates a thin film on the surface of gas sensors - inside the gas detector - and it is not possible to repair or correct later. Also seawater HCL  / CL2, SoX, H2S may cause permanent damage to semiconductor gas sensors. Warm oil may also cause permanent damage to gas sensor, and if installed in kitchen be careful with position.
 

Be careful not to cover the gas detector - free airflow is necessary for correct operation. Do not install gas detector on a surface exposed to vibrations or shock. Gas detector can react and create false alarms if high concentration of alcohol vapours are present in room, gases from aerosol & spray bottles e.g. Hair spray etc. chemical cleaning substances eg.

 
Sensor surface must be cleaned with a dry cloth from time to time, whenever necessary.  
 
Gas detectors are intended to give early warning of an accidental release of - or accumulation of gases. It is always advisable to use redundancy with two individual gas detectors positioned at different levels in a room. Gases may collect in pockets and may not be seen if only one gas detector is used.
 
Gas detectors operate within a circle of max. 4M radius. This covers approx 50 sq, metres. However when installed on a wall, the area is reduced to ½ = 25 sq, metres. This is important to notice.
 
Manufacturer
Con.Da electronics, Copenhagen – Denmark

ek@get2net.dk