We design highly effective toxic shelters that reduce risk to occupants. Our SIP 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. BakerRisk’s toxic shelter assessments quantify infiltration rates, HVAC isolation reliability and timing, and characterize the reliability of the fallback plan.
Our SIP design experts are experienced in:
- Toxic gas detection and HVAC system and exhaust fan isolation
- Isolation of ventilation (dampers) and other major leak paths
- Multi-barrier shelter designs
- Barriers that are highly resistant to infiltration
- Purge, scrubbing, filtering, and pressurization system designs
- Highly effective fallback (evacuation) plans
We have extensive experience in testing and evaluating the effectiveness of SIPs. Our experts can:
- Characterize the timeliness and reliability of toxic gas detection and HVAC system and exhaust fan isolation
- Quantify the infiltration rate into a building or into a room within a building by conducting tracer gas testing or blower door testing
- Characterize the effectiveness of the fallback plan
- Identify weaknesses / areas for improvement in an existing SIP and the fallback plan
- Suggest changes to improve functionality of the SIP and safety of SIP occupants
To ensure that the SIP 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.
Shelter-In-Place Design
Our approach to SIP design incorporates critical aspects to ensure that it 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.
We have developed SIP designs without functional windows and that include toxic gas detection at the HVAC inlet with interlocks that isolate depending on building specifics. The SIP will typically 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 may require purging, scrubbing, filtering, and/or pressurization to effectively mitigate potential toxic impacts. We have the 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.
SIP Assessment
Determining an SIP’s infiltration rate in a given configuration is a critical aspect of a proper SIP 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 uses carbon dioxide) into the SIP volume being tested and measures the concentration decay over time. The rate of concentration decay is used to determine the air-change rate for the specific conditions under which the test was done.
A Blower Door Test set-up in a standard personnel door
A blower door test uses a variable speed 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 American Society for Testing and Materials (ASTM) “Standard Test Method for Determining Air Leakage Rate by Fan Pressurization” (ASTM E779-99) when performing these tests.
An example of infrared image and visual image pair showing the leakage areas around the frame of a personnel door
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.
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