Important HSE calculations and definitions

Lost Time Injuries (LTI)

Any absence from work related Fatalities, Permanent Total Disabilities, Permanent Partial Disabilities and Lost Workday Cases. Total Lost Time injuries are the sum of Fatalities, Permanent Total Disabilities, Partial Total Disabilities and Lost Workday Cases. Restricted Work Cases and Medical Treatment Cases are not included in LTIs.

Lost Time Injury Frequency (LTIF)

The number of Lost Time Injuries (LTIs) per 1,000,000 (million) hours worked.

LTIF = Total LTIs x 1,000,000

               Exposure Hours

Lost Time Injury Severity (LTIS)

A measurement of the seriousness of injuries and is the number of lost workdays (estimated where necessary) per million exposure hours worked during the period.

S = Lost Workdays x 1,000,000

              Exposure Hours

Lost Workday Case (LWDC)

Any work related injury or illness, which renders the injured person temporarily unable to perform any regular job or restricted work within 24 hours of the moment that that the occupational injury was received or illness determined.

The criteria "24 hours" include rest days, weekend days, scheduled holidays, public holidays or subsequent days after ceasing employment. *

* A Lost Workday Case is not the same as a Lost Time Injury (LTI) LTI) as it does not include fatalities. Also, a single accident can give rise to several lost workday cases, depending on the number of people injured as a result of that incident.

Lost Workdays

The total number of workdays lost through occurrence of occupational injuries/illnesses. *

* In cases where employment is terminated after an Injury/illness occurred (other than fatality or Permanent Total Disability), this would include any previously scheduled workdays lost that were planned prior to termination, or an estimate of workdays that would be lost after termination. In cases of death or permanent total disability no lost workdays are

recorded.

LTI

Lost Time Injury.

LTIF

Lost Time Injury Frequency.

Medical Treatment Case

Any work-related injury or illness that involves neither lost workdays nor restricted workdays but which requires treatment by, or under the specific order of, a physician or could be considered as being in the province of a physician.

Medical treatment does not include first aid treatment (one-time treatment and subsequent observation of minor scratches, cuts, burns, splinters, and so forth, which do not ordinarily require medical care) even though provided by a physician or other registered professional medical personnel.

Permanent Partial Disability (PPD)

Any work related injury or illness which results in the complete loss, or permanent loss of use, of any part(s) of the body or any permanent impairment of function or parts of body, regardless of any pre-existing disability of the injured member of impaired body function. *

* A PPD is not related to the ability of the injured person to do is normal work, e.g. it is classified as a PPD if he has lost a finger, toe, arm, limb, etc. but (upon recovery) is still able to do his normal work or any other work that permits for the partial disability.

Permanent Total Disability

Any work-related injury or illness, which permanently incapacitates an employee from doing any work and results in termination of employment or medical severance.

Reportable Injury

Total reportable injuries are the sum of fatalities, permanent total disabilities, lost time cases, and cases involving restriction of work or motion, medical treatment or loss of consciousness.

Restricted Workday Cases (RWDC)

Any work-related injury or illness, other than a fatality or lost workday case, which results in a person being unfit for full performance of the regular job within 24 hours after the moment on which the occupational injury was received or illness determined. *

* A Restricted Workday Case is not a Lost Workday Case, provided that the person can return to work (any work assigned) within 24 hours after the moment on which the occupational injury was received. A Restricted Workday Case occurs when the injured person is temporarily assigned to do other, less strenuous work e.g.

− an assignment to a temporary job;

− part-time work at the regular job;

− continuation full-time in the regular job but not performing all the usual duties of the job.

Where no meaningful restricted work is being performed, the incident is recorded as a lost workday case (LWDC).

Societal Risk (SR)

Societal risk is generally used to describe multiple injury accidents/fatalities, or to describe risks to ‘unnamed’ individuals, which could include the public and is usually described by F-N Curves (Frequency vs. Deaths listed in increasing order of magnitude, 10, 100, 1000 etc.). Societal Risk may also be calculated as a single value known as “Expectation Value” (EV) or “Potential Loss of Life” (PLL), which is given by the expression:

SR = Σ Frequency of hazard occurring X Proportion of time person(s) are exposed X Number of people exposed X Vulnerability

STEL

Short Term Exposure Limit. Limits established by the ACGIH that represent the maximum concentrations workers can be exposed to for 15-minute periods without suffering adverse effects with certain excursion limits.

SWL

Safe Working Load.

TLV – Treshold Limit Value

ACGIH defines three categories of TLVs as follows (* see note):

a) Threshold Limit Value - Time-Weighted Average (TLV-TWA): the time weighted average concentration for a conventional 8-hour workday and a 40-hour workweek, to which it is believed that nearly all workers may be repeatedly exposed, day after day, without adverse effects.

b) Threshold Limit Value – Short-Term Exposure Limit (TLV-STEL): the concentration to which it is believed that workers can be exposed continuously for a short period of time without suffering from:

1) irritation,

2) chronic or irreversible tissue damage, or

3) narcosis of sufficient degree to increase the likelihood of accidental injury, impair self-rescue or materially reduce work efficiency, and provide that the daily TLV-TWA is not exceeded.

A STEL is a 15-minute TWA exposure which should not be exceeded at any time during a workday, even if the 8-hour TWA is within the TLVTWA.

c) Threshold Limit Value –Ceiling (TLV-C): the concentration that should not be exceeded during any part of the working exposure.

Note: The above are abbreviated versions of the ACGIH definitions.

Total Reportable Injury Rate (TRIR)

The number of reportable injuries (Fatalities + Permanent Total Disabilities + Partial Total Disabilities + Lost Workday Cases + Restricted Work Cases + Medical Treatment Cases) per 1,000,000 hours worked. TRIR does not include First Aid Cases.

Total Reportable Illness Frequency

The total reportable illness frequency is the number of total reportable

illnesses per million working hours worked during the reporting period. Thus

Total Reportable Illness Frequency = Total Reportable Illnesses

                                                               Total Working Hours         x 1,000,000

TWA

Time Weighted Average.

BLEVE

A boiling liquid expanding vapour explosion is typically the result of fire engulfing a pressure vessel containing volatile flammable liquid. When the vessel fails the remaining contents burn in an intense fireball.

Bloodborne pathogen

Pathogenic microorganisms that are present in human blood and can cause disease in other humans.

Carcinogen

A substance either known to cause cancer or classified as having a high probability of causing cancer, that is classified by IARC as Category 1 or Category 2. The ACGIH TLV committee classifies as ‘human carcinogen’ or ‘suspected human carcinogen’.

Classification of Hazardous Areas

In industry, with the exception of mining, areas that are hazardous, so far as flammable gases and vapours are concerned, are classified according to the probability of occurrence of explosive concentrations of gas or vapour. These classifications, called zones, are as follows:

Zone 0 is a zone in which a flammable atmosphere is continuously present or for long periods.

Zone 1 is a zone in which a flammable atmosphere is likely to occur in normal working.

Zone 2 is a zone in which a flammable atmosphere is unlikely to occur except under abnormal conditions and then only for a short time

Environmental Impact Assessment (EIA)

Systematic process of evaluating the environmental impacts of an activity or process on the environment.

Hazardous Waste

Wastes may be defined as hazardous on the basis of waste characteristics

(e.g. Flammable, Ignitable, Toxic, Mutagenic, Reactive, Corrosive, etc.) or

waste may be defined as hazardous on the basis of 'Listing' (i.e. are any

components of the waste stream listed as hazardous; in US EPA, or other 

valid classification system).

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