Embryonic Stem Cells


Mayfly Odor Laboratory Offers An Alternative To Dilution To Threshold Evaluations (Do Your Own)

The evaluation of odor samples to determine how much dilution to threshold air may be required of a source can be an expensive and tedious task. Often during the initial planning stages of an odor control project, or in estimating scrubber removal efficiency, a full odor panel assessment may not be necessary. Several clients approached Mayfly Odor Laboratory asking if there was a way that we could provide them with a quick estimate of a samples’ dilution to threshold. They wanted to use the data as rough estimates of what may be required for odor control equipment or to determine how effectively their pilot plant was working. We proposed the following procedure for those clients submitting samples for volatile organic compound (VOC) characterization. We have had a good response to the results and so we are now making it available as an analytical option. A sample is first analyzed by our normal VOC procedure for odor compound characterization with gas chromatography / mass spectrometry (GC/MS) analysis. A sample of the odorous air in a Tedlar bag is then taken outside into ambient air. Two experienced Mayfly staff then perform a series of approximately 50 % dilutions in the bag, refilling with carbon-filtered air each time. The dilutions are continued until the odor is barely or non-perceptible to the staff. The bag containing the diluted air is then returned to the laboratory and reanalyzed. The ratio of full strength compound concentration to diluted concentration is then calculated. This procedure gives the engineer an estimate of the type of compounds and their individual dilution range that would be required to reach a potential odor threshold. It should be noted that this is not a replacement, or equivalent to, full odor panel testing. However, when full panel testing is not required, this procedure offers a possible substitute and gives additional information regarding odor compound concentrations for engineering purposes. (Or Do Your Own)It is always preferential to have your own on-site staff whose familiar with and trained to detect odors from your various sources. To give their assessments credibility and confirmation it is desirable to have an outside source corroborate their findings. Using the same principles as described above on your site, take two Tedlar bag samples of the reference odor. You then move to a no odor area and allow your sensing abilities to recover from being in a strong odor source area. Take one of the duplicate 2-3 L Tedlar bags containing the odor and squeeze about half of the air out of the bag. Attach an air squeeze bulb to a jumbo charcoal tube (CCT) that has had its end seals broken. Attach tubing to the other end of the CCT and attach that end to the Tedlar bag. Refill the Tedlar bag with air by squeezing the rubber bulb and pushing air through the CCT. Retest the diluted odor by placing the outlet valve by your nose and squeezing the air in the bag sample into your nose. Be careful not to overwhelm your senses when the bag odor is still concentrated. There is no need to keep tract of the amount of dilution air as the undiluted sample in the first bag gives us the initial concentration. Continue this procedure until you can barely or no longer detect the odor in the bag. Then send both bags to Mayfly Lab for reduced sulfur and/or volatile organic odor compound analysis. The concentration of the compounds in the undiluted odor air sample will be divided by the concentration of the diluted air sample to give you an estimated DT value for each compound or class of compounds. Materials to perform these procedures are available for purchase from Mayfly Laboratory. Mayfly staff can confirm your odor evaluation if requested. This procedure was posted on our web site in February 2003. There is ongoing work in this area. If you have any interest in these projects, please contact us for additional information 

Residual Paint Odors Can Be Persistent and Potentially Cause Asthmatic Reactions

Over the last few years Mayfly Odor Laboratory has received a significant number of samples for odor investigation regarding residual paint odors in homes. Many of these complaints can be traced to the use of higher molecular weight solvent systems that have replaced older more volatile solvents historically used within the industry. These newer molecular weight solvents have a tendency to off-gas at lower concentrations over longer periods of time in the homes in which they are used. Mold and mildew resistance has also received additional attention by manufacturers. Some suppliers have introduced new mold and mildew resistant formulations in their product lines. As these paints are basically slower drying, the opportunity for ambient levels of ozone and humidity to react with them is increased. When quality assurance issues arise and the paint product develops an off-odor the results can be, at the very least, a serious nuisance odor issue. The following sections discuss an indoor air quality case which is one that we responded to last year and is an example of homeowner problems that can develop. 

The State of Rhode Island Health Department referred a homeowner whose school age daughter was experiencing asthma symptoms for the first time in her young life. The respiratory problems that developed coincided with the remodeling of her room. Mayfly Odor Laboratory staff responded to the home after the owners had experienced problems for several months. Initial discussions revealed the following timeline of events. The paint was purchased in September of 2001 to be used in the home remodeling project. The product, a trim paint, was used on window casings and wood trim at the very end of the room restoration project on April 4-5, 2002. The paint odor was allowed to dissipate for several days. After approximately one week with the odors no longer present, the daughter was allowed to fully reoccupy the room. Near the end of April, during Easter break, unusually warm weather allowed the windows of the room to be opened. A new odor developed in the room with the influx of fresh air. The daughter began to develop asthma symptoms in conjunction with the presence of the odor. Samples of the suspect trim paint were delivered to a hardware store representing the supplier in late April. A draw down card was prepared. In mid-May the supplier reported that there was no odor in the paint. Again in mid-May the manufacturer’s representative came to the home and picked up a piece of trim paint on the window molding from the home. The representative suggested a resealing product for the trim and that it then could be repainted. On the first of June the sealer product was purchased and on the 4th of July applied to the trim. The odor became worse. Mayfly Odor staff were contacted in mid-July and responded to the complaint on 7/19/02. 

Analysis of air, painted surface emissions, bulk painted materials and paint samples were taken on 7/19/02 to identify potential residual paint odor compounds that may be present in the child’s room at the residence. Laboratory results determined that the materials in the room were still off-gassing several compounds from painting activity that had occurred during the previous months, as early as April 2002. Phenoxy-ethanol (EPH) and the two unknowns that resemble the compound 2-methyl, 3-hyroxy-2,4,4,trimethyl phenyl ester of propanoic acid (TPEP) were tentatively identified in the air at 12 and 240 ppb respectively. These levels were detected in the child’s room on the day of the survey even though the room was well ventilated prior to the survey. These same compounds were positively identified in the original paint and in the headspace samples of the treated and untreated wall moldings. The presence of these residual paint compounds in the room represent a potential source of odors and/or irritation to the resident(s) of the home residing in the room. All newly painted materials in the room were removed including sheetrock, wood trim and moldings. Bedding and some other cloth materials had to be replaced as residual odors had permeated them. 

Some of the issues related to the off-odor incident include:

1) Modern paints have lower volatile organic compounds (VOC) and higher molecular substitutes that are more persistent in the environment. 
2) These new formulations can at times off-gas for several months and be a source of odor and possibly lung irritations.
3) These paints are designed to be safe as applied using OSHA standards. OSHA standards do not apply to private residences, children or immune comprised individuals. 
4) Additional unidentified compounds not discussed here were detected and determined to be off-gassing months after the application. These compounds could not be identified in the 
National Institute of Standard (NIST) Mass Spectrum Library, as they are not in it. Also, the manufacturer is not required to supply information on persistent residues of a product that are only present in minor concentrations of the original formulations.
5) The supplier is not required to take into consideration the reaction of ozone with persistent residues of a product that is only present in minor concentrations of the original formulation 
6) Standard VOC air sampling procedures may not detect these higher molecular weight compounds as they are near or in the semi-volatile range of compounds.
7) The ability of individuals to be able to detect an odor in an environment varies greatly. In this case, assessing an odor on a paint stick or molding in the street should not be confused with the odors that may be present in the room. Analytical data confirmed the presence of solvent residues off-gassing from the painted surfaces and present in the room. This analytical data represents a validation of the complaint. Short of bringing an odor panel trained in detecting or discriminating paint odors into the room, this analytical validation is all that was needed. 

This article was posted on our web site in February 2003. There is ongoing work in this area. If you have any interest in these projects, please contact us for additional information.