Aico alarm signals: beeps, chirps and lights
Aico is the UK arm of Ei Electronics and sells the same alarm series under the Ei model numbers. Its homeowner pages cover the mains-powered alarms most UK homes have; the battery-powered Ei650 series manual on Aico’s site gives the LED and beep table used below. Newer Aico series (3000, 600) use other intervals — see the Ei Electronics pages.
If it is sounding a full alarm: the maker’s emergency instruction
Smoke alarm
Aico: if the alarms are sounding there may be a fire — evacuate, and if in doubt always assume the fire is real (homeowner FAQ). The Ei650 leaflet: check doors for heat before opening, crawl low under heavy smoke, get out and meet at your prearranged place, call the Fire Brigade from a neighbour’s house or a mobile phone giving your name and address, and never re-enter a burning house.
From Homeowner FAQs — Why is my alarm beeping? and Battery Powered Smoke Alarms Ei650 Series — instruction leaflet (Rev 6).
Carbon monoxide alarm
Aico: a sounding CO alarm means carbon monoxide is likely to be present. Turn off any gas appliances, open windows and doors, and leave the property; ring the emergency number of your gas or fuel supplier; do not go back in until the alarm has stopped.
From Homeowner FAQs — Why is my alarm beeping? and Basic Alarm Fault Finding.
Every Aico signal we could source
| What you see | What you hear | What it means |
|---|---|---|
| One red flash about every half a second | Full alarm, loud and continuous | Real alarm: Fire sensed. |
| One red flash about every 8 seconds | Silent | Hush or silence mode: Hushed after a false alarm: the Ei650 is silenced for about 10 minutes at reduced sensitivity. |
| One red flash about every 32 seconds | One chirp about every 32 seconds | Low battery: Low battery on an Ei650: the sealed lithium battery is partly used up and the alarm needs replacing. |
| Two red flashes about every 32 seconds | Two chirps about every 32 seconds | Fault: The smoke chamber has degraded (it tests itself). |
| Two red flashes about every 16 seconds | Silent | Alarm memory: Alarm memory on the Ei650i: the alarm went into alarm some time in the last 24 hours. |
| No light named by the maker | One chirp about every 60 seconds | Low battery: On a 140RC series mains alarm the 9 V back-up battery may be running low. |
| No light named by the maker | One chirp, no fixed interval | Fault: There may be a problem with the wiring. |
| Red light | Full alarm, loud and continuous | Real alarm: Carbon monoxide is likely to be present. |
Sources
Aico’s own documents only, read on the date shown.
- Aico: Homeowner FAQs — Why is my alarm beeping? — Aico mains and CO alarms, incl. 140RC series (FAQ). www.aico.co.uk Checked 2026-09-29.
- Aico / Ei Electronics: Battery Powered Smoke Alarms Ei650 Series — instruction leaflet (Rev 6) — Ei650, Ei650C, Ei650W, Ei650i. www.aico.co.uk Checked 2026-09-29.
- Aico: Basic Alarm Fault Finding — Aico alarms (trade fault-finding page). www.aico.co.uk Checked 2026-09-29.