A

-

Seriously defective

Defective

Not satisfactory

Satisfactory/NA

HHSRS VERSION 2

SEPTEMBER 2004

CARBON MONOXIDE

Vulnerable group

Related hazards

A) Living room window

All ages

Fire, Nitrogen Dioxide etc

HHSRS VERSION 2

Multiple locations

Yes

No

Secondary hazards

Yes

No

B) Plan of living room and conservatory

rear yard

DIY built

kitchen

conservatory

A) Gas fire in living room

rear living room

gas

fire

radiator

DESCRIPTION OF HAZARDS

Dwelling: c. 1900 two-storey terraced house

A) Gas fire: The sole source of heating in the principal rear living room is by a fixed gas fire, which has

a back boiler serving radiators in three other rooms. The central radiant has burnt through and the

fire burns with a reddish flame. (The cooker in the kitchen is electric)

B) DIY built Conservatory: The part of the rear yard alongside the back addition has been enclosed,

with a corrugated plastic roof and timber studding supporting single fixed glazing. There is no

direct ventilation to the rear ground floor living room and the only opening light in the casement

window is at high level, the bottom two and one of the upper opening lights having been sealed up.

The only external opening to the conservatory is the door.

LIST OF RELEVANT MATTERS

LIKELIHOOD & OUTCOMES

# Secondary hazards

-

None

Key

3

2

1

-

A

3

-

3

3

1

3

-

-

0

-

3

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 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 non-HMO dwellings.

HHSRS VERSION 2

SEPTEMBER 2004

HEALTH AND SAFETY RATING SYSTEM SCORES

Pre 1920 House

LIKELIHOOD

1 in

6

Low

High

Average: 1,150

Example

6

< 4200 2400 1300 750 420 240 130

75

42

24

13

7.5

4

2.5

1.5 >

Justification

OUTCOMES

Class I

Class II

Class III

Class IV

Justification

RATING

There is no provision for permanent ventilation to the back boiler in the rear room and

the gas fire shows signs of incomplete combustion. In practice, although the DIY

conservatory is not particularly air tight, the rate of air change is likely to fall well below

currently recommended standards when the windows and kitchen and conservatory

doors are closed. Consequently, with the incomplete combustion, the risk is much

higher than average.

%

Average: 0.0

0.1

< 0.05 0.15 0.3

0.7

1.5

3

7

15

26

38 >

Av: 0.0

0.2

< 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

78.2

Score:

<1

0.1

0.2

21.5

78.2

< 0.05 0.15 0.3

0.7

1.5

3

7

15

26

38 >

The evidence of incomplete combustion indicates that there is likely be elevated levels

of carbon monoxide and other gases in the rear room after the fire has been on for

prolonged periods of time. This will increase the risk of fatal, severe and serious

outcomes from these gases and, with the high likelihood, would give a high score of

1,405 and a hazard rating of C.

Example

C

A B

Average: 1

D E F G H

I

J

1405

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 %

Providing permanent ventilation to the back boiler and gas fire and repairing the

installation such that the appliance satisfied the relevant Gas Safety (Installation and

Use) Regulations would reduce the likelihood and health outcomes to average or

below. This would reduce the rating to Band J.

Improved