Chemical disaster or war survival

Chemical dangers are not widely known. People often have no awareness about these dangers that are unavoidable. Dangers come from various industries, fire disasters, volcanoes, and possibility of chemical war. The only sure way to protect oneself or family is evacuation from disaster zone or evacuation to the shelter capable to survive such disaster. To do that, real-time situation awareness about winds and contaminations involved is needed. It may not be available until you end up in a contaminated place. Personal chemical protection may be important factor for survival and reduction of health effects until safe place is reached.
First signs of disaster can be given out by pets as some of them can smell extremely small concentrations of chemicals that humans may not be aware at all. Other signs may be dying or discolored vegetation, strange smell, animals acting in unusual ways and some chemical sensors (like carbon monoxide alarm) going off without any reason.

Danger depends on chemical which is involved. Different disaster causes can have different outcomes and thus for each of them preparation or planning in advance may be needed.

Volcanoes emit poison gases most of which are acidic and dangerous dust. Gases include sulfur dioxide (SO2), carbon monoxide (CO), hydrogen sulfide (H2S) and numerous other. Volcano gases have high carbon dioxide (CO2) content, may be extremely hot in the vicinity which makes any filtration system useless. Acid gas and CO filters may help in some less severe situations, reduce health effects and save lives. Casualties from poison gases alone are close to 3%. Volcano dust is extremely dangerous and improved particle filter is a must at any distance where dust can travel.

Uncontrollable fires are extremely dangerous in towns, cities and near chemical storage areas (like pesticide, herbicide) as there they can cause widespread chemical contamination. Some of these fires may not be so poisonous by themselves (as hot gases rise up) than fallout from them on the soil which later can end up in food or drinking water. Chemical air filtration can be used during fires as long as air has low CO2 content, high oxygen (O2) and filtration offers protection against CO and hot air. Improved particle filter is also needed.
Shelters usually are made with fire hazard in mind as war is direct cause for uncontrollable fires. Although depth, thermal protection and air supply must be taken into account and reviewed. Shelters that are in the forest, urban areas that can easily burn for extended time periods are at risk as fire can heat up ground, entrance significantly. Plastic or rubber parts can melt or burn with all the consequences. Shelters not deep enough may become too hot from fire raging above. Air supply from above during fire may not be possible and adequate air supply for such event is needed.

Some disasters can disrupt electrical grid and are directly dangerous for industries that use cooled liquid gases. These gases can be flammable like methane (CH4) and have a risk of explosion, can cause fires, others are poisonous like liquid ammonia (NH3), SO2, chlorine (Cl2). With electrical grid down, and without backup energy source such gasses will eventually heat up and start evaporation. Air filtration may help with such disasters.

Air filtration can only reduce particle and chemical concentrations. Areas with high contamination concentrations can lead to filtration failure. When contaminants from passing air are absorbed in the filter, with time contamination leaking through filter is gradually increasing. The more polluted is air, the less protection time is left for such filter.
CO or catalyst filters work in a different way, they usually transform chemicals into non dangerous form by oxidizing and either use O2 or chemicals in the filter. Some catalyst filters have long life spans, but have a need for high temperatures to effectively operate. Personal CO filters have usually short limited lifespan.

Personal filters have limited weight and limited lifespan ranging from 20min to several hours (or more depending on chemical contaminant and concentration, filter used) after which filter must be changed or safe place reached. It is possible to calculate time of protection when contaminant concentration is known. Chemicals and their concentration detecting devices may be extremely handy in such situation as they can help to determine when to change filter without being poisoned.

From
[link to en.wikipedia.org]
[link to en.wikipedia.org]
and other links

Personal gas mask filters are marked with a letter and number:
AX - Low-boiling (≤65 °C) organic compounds (brown)
A - High-boiling (>65 °C) organic compounds (brown)
B - Inorganic gases (H2S, Cl2, HCN) (gray)
E - Acidic gases (SO2, HCl) (yellow)
K - Ammonia and amines (green)
CO - Carbon monoxide (black)
NOx - Nitrogen oxides (blue)
Hg - Mercury vapors (red)
SX - Specific compounds excluding CO NOx Hg (violet)

A,B,E,K are generic chemical types which may vary and must be specified by the manufacturer. Number after letter represents filter capacity class

With 30L/min air flow filter must pass test with various chemicals
Class 1 - low capacity, <1000ppm
A1 C6H12 >70min, leaking <10ppm
B1 Cl2 >20min, leaking <0.5ppm
B1 H2S >40min, leaking <10ppm
B1 HCN >25min, leaking <10ppm
E1 SO2 >20min, leaking <5ppm
K1 NH3 >50min, leaking <25ppm

Class 2 - medium capacity, <5000ppm
A2 C6H12 >35min, leaking <10ppm
B2 Cl2 >20min, leaking <0.5ppm
B2 H2S >40min, leaking <10ppm
B2 HCN >25min, leaking <10ppm
E2 SO2 >20min, leaking <5ppm
K2 NH3 >40min, leaking <25ppm

Class 3 - high capacity, <10,000ppm
A3 C6H12 >65min, leaking <10ppm
B3 Cl2 >30min, leaking <0.5ppm
B3 H2S >60min, leaking <10ppm
B3 HCN >35min, leaking <10ppm
E3 SO2 >30min, leaking <5ppm
K3 NH3 >60min, leaking <25ppm

Particle filtration is marked P (white):
P1 - Filters >80% of airborne particles
P2 - Filters >94% of airborne particles
P3 - Filters >99.95% of airborne particles

Particle filter protects not only against dust and aerosol particles, but also is a primary protection from radioactive particles.

There is also similar marking for disposable masks
FFP1 - Filters >80% of airborne particles
FFP2 - Filters >94% of airborne particles
FFP3 - Filters >99% of airborne particles

As an example for marking, chemical filter can be A1B2-P3, which means it protects against organic compounds (A) with class 1 capacity and against inorganic gases (B) with class 2 capacity and against particles (P3).
These classes are generic and can give a hint when choosing filter for certain situation. Filters usually have test data for each chemical separately. It can be used for finding filter change time.
[link to www.osha.gov]

Shelters usually have filters without weight or size restrictions that can last reasonable amounts of time. This time however is limited and can become a problem if air contamination lasts a long time or has much higher concentration than expected. Situation may force to change filters numerous times. Doing it in a way that prevents contamination leakage into shelter is critical.
Whenever air filtration fails, rebreather or pressurized air is needed. Shelters can use compressed air, or O2 supplement and CO2 removal. When air supply finally fails, shelter may have to be abandoned.