• Batteries included (3xAA batteries)
• 5 years battery life and sensor lifespan
• Loud distinct alarm (85 dBA at 3 metres)
• with LED lights to display power and alarm status
• Proven sensor - based on electrochemical technology
• The unit checks the CO concentration every 50 seconds
• At the manufacturer all units are individually calibrated and tested with CO gas to ensure accuracy
• Easy to use Test/Hush button
• Automatic self diagnostics
• Can be tamper-proofed
• Sensitivity: 50ppm (parts per million) CO gas
• Fast CO test mode
• 2 Year Guarantee (limited) 
• Kitemarked to BSEN50291:2001 and CE marked
• Manufactured in Republic of Ireland
• Attractive slimline casing
• View the Kitemark & BS Certificates
• Dimensions (HxWxD): 135x105x71mm

Also see:
Ei205A Carbon Monoxide (CO) Alarm with Memory

This is the technical data for the Carbon Monoxide Detector (with LED) Ei204EN.

Technical Data Sheets

The following technical data sheets are available for this product:

• EI204-Datasheet
• EI204-User-Manual

Q.Does propane gas give off carbon monoxide?

A.Yes, propane is one of the gases that, if not burnt properly, can release carbon monoxide.

Q.I have in my narrowboat a Ei204EN alarm, a strange question but is it possible the alarm would go off whilst my leisure battries are being charged, as last year we went out on our boat and when we got back we plugged the battery charger in to charge the leisure batteries, the alarm went off during the night, this year the same thing has happened, but once the battries are fully charged it wont go off again.
is this possible

A.The electrochemical sensor used in our CO alarms (and by almost every other CO alarm manufacturer) has a cross-sensitivity to hydrogen gas. As hydrogen gas is rarely found in its pure state in a normal household environment it would not cause false alarm problems. However, when lead acid batteries are charged an amount of hydrogen gas is produced in the process and if a CO alarm were to be sited in close proximity it would be quite likely to cause a false alarm.
I know little about how much hydrogen gas is normally produced when charging batteries but I would think that it would be very low levels and this makes me think that perhaps the batteries are being overcharged. I would suggest that this possibility is worthy of investigation.

Q.re co detectors - do these have to be fixed to the wall or is it okay to keep on a window sill?

A.A window sill is considered to be an unsuitable location as it would be affected by draughts and therefore would not function correctly. It is important to have alarms near to sleeping areas to ensure that the alarm can be heard and ideally in every room containing a fuel burning appliance.