Hospital tests showed the victims had high levels of carbon monoxide in their blood while other residents of the flats in Mare Street, Hackney, and paramedics attending the scene also suffered side effects.
An investigation by the Health and Safety Executive discovered Soley Fikret had failed to ensure the three separate boilers and flues in the flats he rented out were checked for safety in the previous 12 months
Mr Fikret was fined £4,000 and ordered to pay £1,500 costs at the Old Bailey, after pleading guilty to two breaches of the Gas Safety (Installation and Use) Regulations 1998.
HSE is now warning other landlords to ensure gas appliances are safe for tenants and properly maintained.
HSE Inspector Gavin Pugh said: 'Landlords must act responsibly. This case should be a warning to landlords who don't bother to look after their tenants. In this instance it was very lucky that no one was killed.
“Had the carbon monoxide poisoning happened slightly later in the night, this incident could have resulted in a terrible tragedy.
'It is the responsibility of every landlord to maintain gas appliances in a safe condition and have them safety checked by a registered gas installer at least once a year, and it is not difficult to arrange for a registered installer to carry out the annual checks.
“Also, it is essential for any new gas appliances, which includes flues and ventilation systems to be installed by a registered gas installer.'
An ambulance was called to the flats in Mare Street on the evening of 11 January 2007 after one of the residents was reported to have symptoms of a heart attack.
Paramedics gained access to the flats and took the individual to hospital. Meanwhile other residents of the building were unable to wake another tenant, and another ambulance was called.
Carbon monoxide poisoning was diagnosed and all residents and guests of the property and the paramedics were treated for the effects of carbon monoxide poisoning.
HSE inspectors attended the next day with British Gas investigators, who put warning notices on the gas appliances in one flat.
They returned to the property on the 15 January 2007 to test the boiler and found it was emitting high levels of carbon monoxide
The Gas Safety (Installation and Use) Regulations 1998 say every landlord must ensure gas fittings and flues are maintained in a safe condition and are checked every 12 months.
For further information on the duties of landlords, letting agencies, tenants and owner occupiers, in relation to the safety of gas appliances click here.