CARBON

Vulnerable age

Related hazards

HHSRS VERSION 2

SEPTEMBER 2004

MONOXIDE

All ages

Fire, Nitrogen Dioxide, Explosion

HHSRS VERSION 2

Multiple locations

Yes

No

Secondary hazards

Yes

No

A) Gas instantaneous water heater

DESCRIPTION OF HAZARDS

A) Location in kitchen/diner

Dwelling: Non-self contained flat in 1890's house

Background: This hazard is in a three-storey, Victorian terraced house, converted into four non

self contained flats and heated by old electric convector heaters. There are two shared bathrooms,

one with a w.c., and a second separate w.c.

Water heater: The photographs are of the 1st floor rear kitchen/diner, which connects directly with

the bedroom, and show the sink with a gas instantaneous water heater over and the adjacent gas

cooker. A crude metal plate and horizontal cowel have been fixed on the wall above the unflued

water heater but this has not prevented the wall and ceiling above becoming stained by the hot

gasses emitted. The window is a double hung sash and there is no other means of ventilation.

There are no carbon monoxide detectors in the dwelling.

A)

LIST OF RELEVANT MATTERS

LIKELIHOOD & OUTCOMES

# Secondary hazard

-

None

Key

3

2

1

-

1

a

b

c

d

e

f

g

h

i

j

Open flued appliances

Flueless appliances

Disrepair to appliance

Inadequate ventilation

Disrepair to ventilation

State of flues

Disrepair to flues

Flue outlet siting

Extractor fans

Ventilation lobby

CO Detectors

A

-

Seriously defective

Defective

Not satisfactory

Satisfactory/NA

A

-

3

3

2

-

-

-

-

-

-

3

A B C D E F G H

I

J

Average likelihood, outcomes and HHSRS score for carbon monoxide poisoning for all

persons in pre 1920 HMOs.

HHSRS VERSION 2

SEPTEMBER 2004

HEALTH AND SAFETY RATING SYSTEM SCORES

Pre 1920 Non s.c. Flat

LIKELIHOOD

Low

High

1 in

18

Example

18

24

13

7.5

4

2.5

1.5 >

Average: 1,410

< 4200 2400 1300 750 420 240 130

75

42

Justification

OUTCOMES

Class I

Class II

Class III

Class IV

Justification

RATING

From the extent of the staining of the walls and ceiling and its pattern around the metal

cowl and decorative plate, this unflued water heater is clearly emiting a substantial

volume of hot and potentially dangerous gases. With no permanent fixed ventilation,

the build up of carbon monoxide and other toxic gases in the room and adjacent

bedroom from both the gas cooker and water heater is likely to be considerable.

Consequently, the likelihood of the occupants suffering some harm will be high.

%

Average: 0.0

0.1

< 0.05 0.15 0.3

0.7

1.5

3

7

15

26

38 >

Av: 0.0

1.0

< 0.05 0.15 0.3

0.7

1.5

3

7

15

26

38 >

Av: 2.0

21.5

< 0.05 0.15 0.3

0.7

1.5

3

7

15

26

38 >

Av: 98.0

77.4

Score:

<1

0.1

1.0

21.5

77.4

< 0.05 0.15 0.3

0.7

1.5

3

7

15

26

38 >

The build up of carbon monoxide and other toxic gases in the room and adjacent

bedroom increases significantly the risk of a fatal, severe or serious outcome.

Together with the high likelihood, this gives a score of 512, a hazard rating of Band D-.

Example

D-

A B C

Average: 1

E F G H

I

J

512

Score

RATING SCORES AFTER IMPROVEMENT

IMPROVE

Justification

NEW RATING

Av (Nos):

Likelihood to

1 in 1,800

Outcomes to

0.0

0.0

2.2 97.8 %

Replacing the gas heater with a modern appliance with a balanced flue conforming to

the relevant Gas Safety (Installation and Use) Regulations would reduce the likelihood

and spread of outcomes to average for the type and age of dwelling, but not below due

to the remaining gas cooker. This would lower the rating to Band J.

Improved