Date: 13 December Mr. Roger Slegt Site Lead Safety Engineer Rotterdam Refinery and Aromatics Plant ExxonMobil Chemical Holland B.

Transcription

1 ExxonMobil Research and Engineering Company 3225 Gallows Road Fairfax, Virginia Telephone Fax Raymond G. Hinske Safety, Civil and Marine Section Date: 13 December 2013 Mr. Roger Slegt Site Lead Safety Engineer Rotterdam Refinery and Aromatics Plant ExxonMobil Chemical Holland B.V Review of the Basis of Firefighter Exposure Limits used by Dutch Regulators for Industrial Firefighting 2013SR 55 Transmitted by Dear Roger, Per your request, attached please find the EMRE Review of the Basis of Firefighter Exposure Limits used by Dutch Regulators for Industrial Firefighting. The attached report (and not necessarily the cover letter) has been reviewed by the appropriate individuals in Legal and Public and Government Affairs in order to release the document to outside organizations, including Dutch Regulators. If you have any questions, please do not hesitate to contact myself (contact information above) or Brian Thomas ( ). Regards, Raymond G. Hinske

2 CC: ROTTERDAM Jan-Willem Briet, ExxonMobil Chemical Holland B.V Marloes Brands, Legal Counsel, Esso Nederland B.V. Remko Kruithof, Public Affairs Manager, Benelux EMRE / FAIRFAX Cathy Pincus, EMRE Process Safety and Risk Section Head Sohiel Ghassemi, EMRE Process Safety and Risk Brian Thomas, EMRE Process Safety and Risk Erica Jones, EMBSI Industrial Hygiene Associate Glenn Barrett, Counsel, Downstream Law Department Laura Keating Brannen, Downstream Advisor, Public and Government Affairs

3 EMRE Engineering Equipment Technology Division E x x o n M o b i l R e s e a r c h a n d E n g i n e e r i n g C o m p a n y REVIEW OF THE BASIS OF FIREFIGHTER EXPOSURE LIMITS USED BY DUTCH REGULATORS FOR INDUSTRIAL FIREFIGHTING 2013SR 55 December 13, 2013 ExxonMobil Research and Engineering Company ( EMRE ) was requested by ExxonMobil Chemical Holland B.V. and Esso Nederland B.V. (together ExxonMobil NL ) to conduct a literature search and evaluation of maximum personnel radiation exposure limits, specifically related to emergency responders. The basis for the request was a request from Dutch regulators to comply with the 3.0 kw / m 2 limit currently set forth in non-binding Dutch regulations. The results of this review are included in this report. Research into existing recommended exposure limits generally focuses on direct skin exposure to thermal radiation, where the target organ is the skin, and the resultant injury is a burn, indicating that thermal radiation can create a dermal exposure concern that needs to be considered. However, while not specifically evaluated in this review, history has shown that in general, firefighters working behind a waterwall in firefighter bunker gear are not generally at significant risk from thermal radiation burns, and that risk is generally well managed. The values used by API 521, Table 9 (recreated below) have been used around the world in petroleum industry design, and have historically been effective for short term, emergency flare relief exposure. While this table was intended for exposure to thermal radiation from flares during emergency depressuring events, the table can be used as an indication of safe exposure for emergency response personnel and operators during emergency events, and can be used as a guideline for emergency responders conducting short term activities during fire events. As part of the evaluation, EMRE evaluated TNO Report TNO-DV C024 Veilige stralingscontouren bij incidenten - gerelateerd aan warmtebelasting voor hulpverleners (Safe radiation contours incidents - related to heat load for workers). EMRE understands that this TNO Report is the basis for Dutch Regulatory Document PGS-29, Regulations for Above Ground Tank Storage. TNO Report TNO-DV C024 concludes that Based on the THDYN simulations, there is no direct reason to change the radiation contours of 3 kw/m2 for fire fighters or 1 kw/m2 for other emergency responders. Several things are apparent when looking at TNO-DV C024:

4 1) TNO-DV C024 is based on the use of the THDYN models, and not on personal exposure studies or the results of historic exposure evaluations. More importantly, the THDYN model appears to be based on the steady state heat load on individuals, which takes into account activity load, clothing, temperature, radiant heat, etc, as well as individual factors such as body condition, weight, acclimation, etc. The THDYN model also uses individual characteristics to help predict when an individual will be susceptible to the hazards associated with elevated core body temperatures. 2) The THDYN Model details are documented in TNO Report TM-97-B007 Thermal Modeling of Individual Characteristics. Upon review of TM-97-B007, it is apparent that the THDYN model is looking at the steady state effects of cumulative heat load (work stress, environmental factors, etc) on the core body temperature of individuals based on specific factors of individuals (weight, conditioning, acclimation, etc.). Figure 2 from TM-97-B007 is recreated below to graphically demonstrate the factors indicated above that are considered in the THDYN model. The factors that are included as part of the model create a heat balance on the individual. That heat balance, assuming steady heat inputs that are within the capability of the individual to provide cooling, will ultimately reach a steady state core body temperature. While this evaluation did not attempt to determine the appropriate core body temperature that should be used as a maximum, TM-97- B007 suggests that 39.2 o C is an appropriate maximum core body temperature. If the heat inputs are not within the ability of the individual to provide cooling, then the potential exists for significant injury due to overheating of the individual.

5 3) TM-97-B007 also indicates that it takes some amount of time for the core body temperature to achieve a steady state temperature, or for the core body temperature to increase above the temperature of concern (in this case, 39.2 o C). While there does not appear to be a specific scenario directly related to firefighting, in several examples documented in the report, it will take several minutes in a heat stress environment once the individual begins to exercise for the core body temperature to either reach a steady state or to rise above the temperature of concern. Figure 9 from TM-97-B007 below demonstrates one such scenario where the lower graphs indicate the individual was able to reach steady state temperature, and the upper graphs show a scenario where they were not and would likely sustain heat related injury. 4) TNO Report TNO-DV C024 specifically does not include the potential for the skin as the target organ for thermal radiation, as the THDYN model, which is the basis for the report, does not attempt to model dermal exposure. As indicated earlier, most historic research associated with thermal radiation is based on skin / dermal exposure and a resultant burn, not on core body temperature load. While this was discussed in several locations throughout the article, the English summary states that The current version of the THDYN model does not allow for prediction on local skin temperatures and this issue was not considered further in this study. 5) TNO Report TNO-DV C024 recognizes that activities at elevated thermal radiation levels are possible without overheating of most individuals. The English summary states that At moderate to high exercise levels the work duration is limited to 20 minutes. This does not state that personnel are not permitted to work in areas at or above the specified level. It simply indicates that there is a time component to keep firefighters (or working individuals) from overheating if they are working in elevated levels of thermal radiation. 6) The THDYN model appears to be based on extended work activities in a hot (or heat stressing) environment. It does not appear to address very short term activities in such an environment. The THDYN model appears to recognize that it takes the body some amount of time to either reach a point where the individual can manage the heat load (steady state), or for the core body temperature to rise above a level that would be considered dangerous, but this time does not appear to be taken into account when regulatory maximum exposure limits were defined. 7) There is no evidence in TM-97-B007 that the THDYN model incorporates any radiation absorption factors associated with clothing, PPE or other physical barriers (such as a firefighter

6 working behind a water wall). While clothing, PPE or other factors may affect the individual s ability to regulate heat and therefore may have a negative (or positive) effect on their ability to regulate heat, the ability of these factors to mitigate radiant heat does not appear to be considered in the THDYN model as discussed in the document. Conclusion TNO Report TNO-DV C024 may prove useful guideline for work activities in hot environments, or for firefighting activities where the duration of the activities is long enough to result in excessive core body temperature. It does not appear to be appropriate for predicting risk to firefighters for all tasks. Based on the information available, the application of the THDYN model to set an absolute radiation limit for a short duration task (such as entry into an area of elevated radiation (>3.0 KW/m 2 ) to operate a manual valve) is inappropriate. The hazard in the case of short term exposure is not excessive core body temperature. A more appropriate short term exposure limit would be one established to protect individuals from burns to skin. As indicated above, the limits identified by API 521 may be more appropriate for short term emergency applications such as hose hookup or valve operation, using the limits and PPE indicated by API as safe for short term emergency exposures. However, the firefighting plans must make the determination if exposure time frames for the activities in question are realistic (i.e. can an activity like hose connections / valve operation be handled within 2-3 minutes at 4.73 kw/m2). It must be noted that the safety of the individual in this case is a function of both radiation level and exposure time so it is important to accurately determine the duration of the task and ensure it is within the allowable duration set out in the standard. The THDYN model maybe a useful tool to determine how long it would take a population to achieve dangerous core body temperatures under certain modeled fire conditions, and these models may be useful in developing the site s firefighting plans, but the straightforward and absolute application of a limit that would be applicable to all scenarios is not appropriate based on the description and basis of the THDYN model.