We design highly effective toxic shelters that reduce risk to occupants. Our shelter-in-place designers have knowledge beyond design specification – they understand critical aspects of a highly effective SIP. A design may start with a blank page, or it may be a modification of an existing building. Furthermore, BakerRisk’s toxic shelter assessments quantify infiltration rates, HVAC isolation reliability and timing, and characterize the reliability of the fallback plan. Whether you need a new SIP or improvements to existing buildings, we can help.
Our approach to SIP design and toxic safe haven construction incorporates critical aspects to ensure that each shelter is highly effective at maintaining a safe environment for the occupants whether the design is for a new SIP or to modify an existing one.
For example, we have developed SIP designs that include toxic gas detection at the HVAC inlet with interlocks that isolate depending on building specifics. An SIP may also include an interior room where personnel would shelter that is highly resistant to infiltration from the rest of the building.
In extreme situations, an SIP or toxic refuge may require purging, scrubbing, filtering, and/or pressurization to effectively mitigate potential toxic impacts. We have expertise in each of these areas and will recommend the most practical approach for your specific situation.
To address the possibility of system failure, building damage (e.g., blast damaged the building and initiated the toxic emergency), or a more severe impact than the SIP can handle, we aid you in developing a fallback plan that includes the critical parameters to ensure that occupants have a high probability of survival even if the SIP is compromised in a critical event. The fallback plan provides an integral part of a facility’s overall toxic emergency response plan.
To ensure that an SIP or toxic refuge minimizes toxic risk to the extent practical, it is important for the shelter design to account for the likelihood and severity of potential toxic release scenarios. Where necessary, we will perform a toxic risk analysis (see FSS/QRA services) to support risk-informed design decisions or utilize results from a prior study. Information from these analyses can be used for safe haven construction and the building of new SIPs when needed.
Types of Assessments
Determining an SIP’s infiltration rate in a given configuration is a critical aspect of a proper assessment. We can perform tracer gas and blower door tests as well as other critical assessments, including obtaining accurate estimates for the timeliness and reliability of HVAC isolation, identifying weaknesses in the shelter design, and characterizing the reliability of the fallback plan, if applicable.
A tracer gas test introduces a safe amount of a non-hazardous gas (BakerRisk typically uses carbon dioxide) into the SIP volume being tested and measures the concentration decay over time. The rate of concentration decay is used to calculate the air-change rate for the specific conditions under which the test was done. BakerRisk performs tracer gas testing according to industry standard American Society for Testing and Materials (ASTM) E741-11.
A blower door test uses a variable-speed, calibrated blower fan and pressure-sensing equipment to characterize a building’s air leakage rate as a function of the pressure difference. These measured parameters determine an equivalent hole size, which is used to estimate an infiltration rate as a function of wind speed. BakerRisk follows the ASTM “Standard Test Method for Determining Air Leakage Rate by Fan Pressurization” (ASTM E779-19) when performing these tests.
Using an infrared camera, BakerRisk can inspect the envelope of your buildings and pinpoint the leakage areas causing excessive air infiltration. The infrared inspection of the building envelope will locate and document abnormal patterns of infrared radiation from the building envelope (exceptions) that could be potential air leakage spots. We determine which of these exceptions is likely convective or caused by cracks or holes in the building envelope and recommend conceptual upgrades to mitigate these problem areas.