Specification of a valid Material Assessment Algorithm

for ACM Robin Howie,

Robin Howie Associates, Edinburgh

BOHS Conference 2016

Managing Asbestos in Premises

HSG227 provides a Material Assessment Algorithm that looks at the type and condition of ACM and the ease with which it will release

fibres if disturbed.

HSG227 Material Assessment Algorithm

Note that the Algorithm does not meet the Regulation 5 duty to default to the assumption that in the lack of

information materials contain asbestos that is not chrysotile

alone.

HSG227 Material Assessment Algorithm - example

Primary day-school classroom with painted AIB ceiling tiles in good

condition.

Scores: Product type-2; Condition-0; Surface treatment-1; Asbestos type,

amosite, -2. Total score 5. Potential to release fibres “Low”

Is the HSG227 Material Assessment Algorithm valid?

If the asbestos were chrysotile or crocidolite the scores would be 4

(very low potential) or 6 (low potential) respectively.

Is the HSG227 Material Assessment Algorithm valid?

But crocidolite and amosite are 500 and 100 times respectively more

potent than chrysotile for causing mesothelioma, Hodgson & Darnton

(2000), and are at least 10 times easier to render airborne, HSC

(2005).

Is the HSG227 Material Assessment Algorithm valid?

The HSG227 algorithm fails to adequately take account of asbestos

type and dustiness.

Is the HSG227 Material Assessment Algorithm valid?

As the HSG227 Material Assessment Algorithm fails to address the Reg 5

duty and fails to adequately take account of asbestos type and asbestos dustiness it is not fit

for purpose.

Outline of a valid Material Assessment Algorithm

The algorithm should be multiplicative and in lack of

information should default to the highest value for each factor.

Condition

Condition Score

Good/Intact, painted surface

x1

Moderate, unpainted surface

x3

Poor x10

Accessibility

Accessibility Score

Out of normal reach x1

Within reach of thrown objects

x3

Within reach without extension

x10

Severity of likely disturbance

Severity of disturbance Score

Low-light abrasion only x1

Moderate-punch, thrown object x3

High-kick, vandalism x10

Maintenance activity x30

Removal activity x100

Nature of matrix Matrix Score

Floor covering in good condition x1

Painted AIB or armouring, AC (demonstrated chrysotile only), painted chrysotile (demonstrated) cloth in good condition

x3

Unpainted AIB or armouring, AC containing amosite or croc, floor covering or chrysotile cloth in poor condition

x10

Insulating slabs, sections, rope x30

Insulating paste, un-armoured x100

Spray x300

Intended use of premises Premises, annual occupancy, most vuln- erable occupants, mean expected AaD

Score

Office or retail, 1,800 hr, adults, 80 yr x1

College residential, 2,400 hr, 18-25 yr-olds, 90 yr

x5

School, day-1,400 hr (residential-3,800 hr), 5-10 yr-olds, 90+

x8 (x20)

Domestic residential, 6,000 hr, pre-school children, 90++

x30

Asbestos type

Type Score

Chrysotile only (demonstrated)

x1

Amosite x100

Crocidolite x500

Relative dustiness

Type Score

Chrysotile only (demonstrated)

x1

Amosite x10

Crocidolite x10

Material Assessment Algorithm - example

Primary day-school classroom with painted AIB ceiling tiles in good

condition.

Scores: Condition x1; Accessibility x3; Severity of disturbance x1; Matrix x3; Use of premises x8;

Amosite x100; Dustiness x10. Total score x 72,000

Material Assessment Algorithm - example

Note that in an office building with the same scores for Condition,

Accessibility, Severity of disturbance, Matrix, Amosite and

Dustiness but Use of premises being an Office the total score would be

9,000; illustrating the increased risk in situations involving children.

Material Assessment Algorithm

As the recommended algorithm complies with the Reg 5 duty and

gives a correct indication of potential risk, it is more fit for

purpose than the HSG227 algorithm.