Odorless gas or chemical hazards in buildings: this article discusses what to do about indoor contaminants that might not smell or give any ready indication of their presence.

This article series provides articles on to diagnose, test, identify, and cure or remove a wide range of obnoxious or even toxic odors in building interiors, building mechanical systems, or in building water supply.

How to Think About Indoor Contaminants that Avoid Detection - Gases or Chemicals that do not Produce a Smell

Our page top photo shows outdoor evidence of a radon mitigation system at a building. Radon is an example of an odorless, colorless gas that at elevated levels can be a health hazard for building occupants.

Question About Indoor Chemical or Gas Hazards that Don't Smell 

I am writing to ask you whether it is true that some chemicals are odorless. The reason for the question is that the smell seems to be dissipating.

However, since we we do not know what the source of the smell was, we cannot know for sure whether the source causing the smell can still be harmful to our unborn baby. -- Jacqueline Saenz, CA.

Answer:

OPINION: Some chemicals are odorless - for example see "Fish Tale" in the New York Times.

The article discussed a type of food poisoning (not a building material or sewer gas issue) associated with unsafe seafood - ciguatera poisoning (eating fish contaminated with a toxin that grown on reef algae) stating

"Unlike most other causes of food poisoning, this toxin is colorless and odorless and isn't destroyed by cooking."

Three Most Common Dangerous Odorless Gases in Buildings

1. RADON HAZARD TESTS & MITIGATION
   
   if your building is over radon-bearing soils and rock, this odorless, colorless gas could be a health hazard. Testing and remediation are well understood and not technically difficult.
2. Similarly, carbon monoxide (CO) gas, can be found in buildings where there is a gas burning appliance or chimney defect, is odorless and colorless.
   
   See CARBON MONOXIDE - CO
   
   

Really?: while CO is odorless, carbon monoxide may be present in flue gases from oil or gas fired heating equipment. Those flue gases may indeed smell - like "gas" or like heating oil.

But in general, if there was an indoor odor present that later dissipated, it was not likely to be one of those particular hazards.

Because your original question (not included above) concerned sewer gas, it would be methane, not CO gas would have been more likely to be detected in your building.

Sewer gas, a complex of gases, is not normally odorless - it smells like sewage, poop, or methane. But sewer gas odors can indeed "come and go" depending on several variables, as we discuss below.

Building Indoor Odors / Smells that Eventually Diminish or Stop Completely

The types of building materials that smell for a while but then stop on their own, with no discover, repair, or removal of the offending source, include:

• New building products - smells that dissipate and do not usually return, material, coatings, especially products that emit VOCs or other gases such as formaldehyde.
  
  Examples of sources of indoor odors that typically diminish or stop entirely include some brands of carpeting, cabinets or shelving made from particle board, furniture (upholstered furniture using certain foam products and possibly even coverings such as a vinyl couch, glues used in applying tile or other ceiling or flooring products, some plywood products, rubber tub mats, sheet flooring (vinyl floors), paints, vinyl or rubber window curtains or shower curtains.
  
  We found a horrible building chemical smell traced to new 6-mil polyethylene plastic that had just been placed on the ground over a crawl space that extended below the structure. See these examples:
  • CARPETING & INDOOR AIR QUALITY
  • FORMALDEHYDE HAZARDS
  • VOCs VOLATILE ORGANIC COMPOUNDS.

Building Odors / Smells That May Come and Go

• Animal smells - odors from visiting animals may eventually dissipate after the pest or pet has been out of the building for weeks or months.
• Heating Equipment, Age, Types, furnaces, boilers, water heaters, if there is a chimney cap or other venting defect, may make odors intermittently in buildings - for example stopping seasonally when the heater is not used.
  
  See BACKDRAFTING HEATING EQUIPMENT.
• Sewer gases - odors from drains may come and go seasonally, or depending on fixture use.
  
  See SEWER GAS ODORS in COLD / WET WEATHER.
• Changes in building conditions can make even a long-lasting odor "come and go", including
  • Variations in building indoor temperature and humidity
  • Variations in weather, building leaks and moisture levels from outside conditions that affect the indoors
  • Changes in building air movement: fans on or off, doors open or shut, windows open or shut, elevators in use or not, stairwells open or closed, different HVAC equipment in or out of use (heating vs cooling), cars running in a garage with a garage door open or shut (watch out for fatal carbon monoxide poisoning)

So How Might we Suspect and Decide to Test for an Odorless Gas or Chemical in Our Apartment?

Luckily, in most cases in buildings and building materials, problem chemicals or gases are delivered in a soup of materials, not in a pure form, and even if the dangerous material is odorless, most often it is in a soup that has an odor. For example,

see BOILER NOISE SMOKE ODORS.

For example, carbon monoxide may be odorless, but if it's being delivered by a chimney leak or a car exhaust, other ingredients in those gases are often noticeable.

Watch out: often does not mean always. If building occupants are asleep during a CO poisoning hazard they could be asphyxiated without ever waking up. That is why it is really smart to have both working smoke detectors and working carbon monoxide detectors in your home.

How can I Check for or Test for Odorless Indoor Toxic Contaminants and Chemicals

OPINION: It is not cost-reasonable to try to test for every possible contaminant in a building, chemical or gas: there are just too many possibilities, and there not any simple inexpensive broad-spectrum "catch all" test.

See TOXIC GAS TEST PROCEDURES. Don't just make a "wild guess" and then just test for that contaminant - doing so may lead to a false sense of security while you may be ignoring a problem that was not detected because it was not looked-for.

Make a Quick Amateur Do-it-yourself Building Contaminant Risk Assessment

Therefore our approach is to decide when further investigation or action is needed (do we need to "hire an expert") based on an initial level of risk assessment:

• Are there building-related occupant complaints? This is a subjective measure but it can be helpful to know if people appear to react with IAQ or health or respiratory complaints when they enter or spend time in a specific building or building area.
• Is there visible evidence of something thought to be a concern, some building condition or building event that often leads to an indoor environment or air quality worry, such as evidence of leaks, mold remediation (was the cleanup performed correctly) or a radon mitigation system (is it working properly?)
• Is there history of leaks from any source that have wet building materials or cavities (possible hidden mold)
  • A sewer backup (bacterial hazards) -
    
    see ODORS, SEPTIC or SEWER
  • Unusual products, such as old chemical bottles
  • Stains, spills that might need explanation
    • MOLD ODORS, MUSTY SMELLS - may be suspected where leak stains mean ceilings or walls have been wet.
      
      At MOLD / ENVIRONMENTAL EXPERT, HIRE ? we describe how to decide if it's appropriate to hire a mold expert.
    • THERMAL TRACKING - indoor stains can indicate an unsafe heating system
• Is there historical evidence that suggests a problem is highly likely though hidden
  • A history of building use and building occupants may disclose prior activities that produced or used unsafe products or chemicals (gases? probably dissipated)
  • A client bought a strip mall; we saw an abandoned trailer on the property - it had been used to store pesticides - turned out not to be a problem, as nothing had leaked;
    
    But later the client called to say that four owners back a tenant had done metal plating and there was heavy metal cadmium contamination in some of the soil - DEC wanted it cleaned up.
    
    No one dreamed this problem was lurking, but a more extensive historical research of building occupants and uses might have raised this question by identifying a metal plating operation years before.
• Is there visual evidence that suggests a problem by "indirect evidence" 
• A client was buying a house; we saw evidence of a history of termite damage but no evidence of professional treatment (drill holes around the perimeter of the concrete floor slab that had been capped);
  
  we did see irregular, angled drill holes in floor framing near termite damage (possible unprofessional pesticide application); there was no record of professional pest control treatment; we took a sliver of wood from a sill plate for mailing to a test lab.
  
  The lab confirmed that a now-banned pesticide, chlordane, had been liberally applied to wood surfaces. Possibly improperly. At a minimum, precautions during renovations were in order.
  
  If there is evidence of a specific concern, or type of concern, then further testing may be in order. If there is evidence of building related complaints, a visual inspection by an expert, combined with history taking about the occupants and the building, and possibly specific targeted tests, may be in order.
  
  See PESTICIDE EXPOSURE HAZARDS.
• Other examples of "indirect evidence" that can lead to important discoveries about conditions at a property are discussed
  
  at DEVELOPING YOUR X-Ray VISION

Other Building Hazards are Latent - Odorless, Colorless, Until an Event: Building Fire or Flood

Other indoor hazards are simply lurking, like a stair-fall: nothing happens until something else happens.

• VINYL CHLORIDE HEALTH INFO discusses possible health concerns from PVC, dioxin, or HCL outgassing that occurs in vinyl building products (siding, windows, trim) are consumed in a fire (and possibly at lower levels from heating such as by sunlight).
• Ozone Odors & Ozone "deodorizers" - sometimes misuse of this equipment actually creates a hazard indoors
• See INDOOR AIR HAZARDS TABLE for a comprehensive list of indoor IAQ concerns

Reader Question: Suspected Chemical Hazards in a Converted Industrial Space: Tetrachloroethylene exposure testing, hazards, MSDS

I got your website address from one of the Dutchess County health inspectors. He tried to help us but he could only test for organic solvents. He said sorry when he could not find anything and told us we needed to hire a private company to do testing.

We moved into a newly converted industrial space at [redacted for privacy] in Poughkeepsie.

The building use to be a metal factory for the last 60 years until they turned it into rental units. On the 5th day of working there I noticed a strange vapor in the air that smelt like "welding" or something.

For about a month after that I was in like a zombie like state. When I felt to sick to go to work and stayed home for a few days I snapped back to myself.

Over those few days I was shaking like I was going through withdrawal or something. I downloaded a list of hazard waste shipments that this metal company shipped out and my symptoms fit well with tetrachloroethene exposure

I called the health dept and they told me to go to the emergency room which they said the only treatment would be fresh air and rest. I guess the health dept meet with the landlord and they were not able to find anything. One day a few days later I was there I could smell the stuff in the air that's when the inspector meet with me and said they can only test for solvents.

I bought one of these Haz Mat smart strips It tested positive for oxidizer and the Cyanide test turned a funky color that is not on the chart.

The landlord is a large company based in Westchester they seem to not care. The keep saying to write down dates and times and get blood tests. They never return our calls We tried to get blood tests but the doctor said we need to find out what we exposure to.

This nightmare has gone on for 2+ months my business is pretty much destroyed. I will be homeless in a month if someone does not help Can you please help us pro-bono or on a payment plan Thanks, R.S. - Poughkeepsie, New York

This question was originally posted

at RENTERS & TENANTS ADVICE for UNSAFE or UNHEALTHY HOME

Reply:

I am sorry to read of the difficulties you describe, and also to report that because my forensic expertise is with particles, mold, allergens, and not chemical contaminants, I'm not the best person to assist you.

I agree that there could be chemical contaminants left from the prior industrial use of your building, including oils and solvents, and on an older building such as those along Cottage St. in Poughkeepsie, even pesticides.

Tetrachloroethene, also referred to as tetrachloroethylene or as "perc" was used in dry cleaning as well as a degreaser for metal working.

Watch out: while it is quite reasonable to suspect that tetrachloroethylene was and may remain present in a building where metalworking was conducted (used as a degreaser solvent that is both volatile and persistent in the environment), it would be a serious mistake to jump to the conclusion that it is the chief or only hazard in your building just as it would be risky to guess at your own exposure or to diagnose your complaint without consulting a qualified expert physician and hygienist.

Just as an example, depending on the kind of work performed, metal plating, for example, can leave other hazards such as cadmium or other heavy metals behind in a local environment.

Watch out: Similarly, the "Smart-Strip" test kit that you purchased is a warning badge intended for emergency responders not comprehensive building surveys for chemical hazards.

It was developed by Mike Reimer[5] and is sensitive to chlorine, abnormal pH levels (identifying highly acidic or highly caustic agents), Fluoride, some nerve agents, Oxidizers, Arsenic, Sulfides, and Cyanide.

Watch out: this test is by no means intended as a broad spectrum analyzer to identify specific chemicals among the thousands that may be used among various industries and industrial processes.[3][4][5]

This chemically reactive "badge" is intended to be used or worn by first responders and emergency workers in the field to make very broad identification of hazardous conditions. It is not intended to identify specific chemicals or contaminants.

And while this badge is widely accepted as a rough hazard screen, with this or many other chemically-based tests for contaminants, the presence of some chemicals or gases will affect the detection of others.

In contrast, an expert building investigator will consider the history of use of the building, the site, even nearby sites, as well as actual onsite observations, and occupant interview results in choosing an approach to screening for specific hazards.

I'm not sure you have to identify the exact solvent or chemical for a physician to be of assistance. If s/he has experience in environmental medicine or can refer you to someone who has that experience, there are most likely somewhat more broad exposure tests to hydrocarbons, solvents, including the one you name.

I suggest contacting an industrial hygienist willing to work on residential exposure questions, or perhaps Paul Ciminello at Ecosystems Strategies. But I am doubtful that many others besides myself are willing to take work like this on a pro-bono basis. And expert services can be costly.

Watch out: In my OPINION the safe inhabitability of a building is the responsibility of the building owner, and more, that the building owners may be inadvertently accepting a very very large liability risk if they have not had the building adequately surveyed and assured safe for occupants.

If you make that concern clear, in writing, you may find that the owners will be willing to have proper inspection and testing performed. We can understand that an owner, not wanting to face or exacerbate what they may feel are avoidable expenses or troubles, may hope to find someone who will be quick, cheap, and who will give a clean bill of health to the building.

But the risks of sloppy, careless or superficial work are so great for both owners and occupants, that in my view that would be a dangerous approach, and one to be avoided.

At RENTERS & TENANTS GUIDE TO MOLD & INDOOR HAZARDS we give advice to renters concerned about mold or other indoor contaminants - that may be helpful to you,

If you think it will assist your building owners in deciding what action is appropriate, when you write to them (phone calls alone are not adequate if serious building risks are suspected) you can include a copy of our correspondence, along with your own description of your concerns, along with

the NEW YORK STATE file about TETRACHLORETHYLENE EXPOSURE [PDF]
that and

the TETRACHLORETHYLENE MSDS [PDF] that I attached to my email to you and link-to here.

Question: could my pool heater be corroded by ozone?

2018/12/31 lmaliver@comcast.net said:

I have had to replace 2 pool funaces because of corrosion of the heat exchanger which is occurring from outside-in as opposed the the usual inside-out.

Notice: this discussion has moved to a new page

at HEAT EXCHANGER CORROSION

...

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• MOLD / ENVIRONMENTAL EXPERT, HIRE ? - when to hire someone
• RADON HAZARD TESTS & MITIGATION
• SICK HOUSE IAQ QUESTIONNAIRE

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